diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc
index 1ff42e5653b..4d76b39d44c 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_cluster_manager.cc
@@ -55,7 +55,7 @@ class XdsClusterManagerLbConfig : public LoadBalancingPolicy::Config {
   using ClusterMap =
       std::map<std::string, RefCountedPtr<LoadBalancingPolicy::Config>>;
 
-  XdsClusterManagerLbConfig(ClusterMap cluster_map)
+  explicit XdsClusterManagerLbConfig(ClusterMap cluster_map)
       : cluster_map_(std::move(cluster_map)) {}
 
   const char* name() const override { return kXdsClusterManager; }
diff --git a/src/core/ext/transport/chttp2/transport/flow_control.h b/src/core/ext/transport/chttp2/transport/flow_control.h
index 42c5986fd93..7e053585b18 100644
--- a/src/core/ext/transport/chttp2/transport/flow_control.h
+++ b/src/core/ext/transport/chttp2/transport/flow_control.h
@@ -201,7 +201,7 @@ class TransportFlowControlBase {
 class TransportFlowControlDisabled final : public TransportFlowControlBase {
  public:
   // Maxes out all values
-  TransportFlowControlDisabled(grpc_chttp2_transport* t);
+  explicit TransportFlowControlDisabled(grpc_chttp2_transport* t);
 
   bool flow_control_enabled() const override { return false; }
 
diff --git a/src/core/ext/transport/chttp2/transport/writing.cc b/src/core/ext/transport/chttp2/transport/writing.cc
index 2ce55d08505..317afcc5103 100644
--- a/src/core/ext/transport/chttp2/transport/writing.cc
+++ b/src/core/ext/transport/chttp2/transport/writing.cc
@@ -198,7 +198,7 @@ class StreamWriteContext;
 
 class WriteContext {
  public:
-  WriteContext(grpc_chttp2_transport* t) : t_(t) {
+  explicit WriteContext(grpc_chttp2_transport* t) : t_(t) {
     GRPC_STATS_INC_HTTP2_WRITES_BEGUN();
     GPR_TIMER_SCOPE("grpc_chttp2_begin_write", 0);
   }
diff --git a/src/core/ext/transport/cronet/transport/cronet_transport.cc b/src/core/ext/transport/cronet/transport/cronet_transport.cc
index 4b5a3ff29a3..b98b6a173f3 100644
--- a/src/core/ext/transport/cronet/transport/cronet_transport.cc
+++ b/src/core/ext/transport/cronet/transport/cronet_transport.cc
@@ -117,7 +117,7 @@ typedef struct grpc_cronet_transport grpc_cronet_transport;
 /* TODO (makdharma): reorder structure for memory efficiency per
    http://www.catb.org/esr/structure-packing/#_structure_reordering: */
 struct read_state {
-  read_state(grpc_core::Arena* arena)
+  explicit read_state(grpc_core::Arena* arena)
       : trailing_metadata(arena), initial_metadata(arena) {
     grpc_slice_buffer_init(&read_slice_buffer);
   }
@@ -151,7 +151,7 @@ struct write_state {
 
 /* track state of one stream op */
 struct op_state {
-  op_state(grpc_core::Arena* arena) : rs(arena) {}
+  explicit op_state(grpc_core::Arena* arena) : rs(arena) {}
 
   bool state_op_done[OP_NUM_OPS] = {};
   bool state_callback_received[OP_NUM_OPS] = {};
diff --git a/src/core/lib/channel/channel_trace.h b/src/core/lib/channel/channel_trace.h
index c26e3016da7..126abc7eb9d 100644
--- a/src/core/lib/channel/channel_trace.h
+++ b/src/core/lib/channel/channel_trace.h
@@ -41,7 +41,7 @@ class BaseNode;
 // https://github.com/grpc/proposal/blob/master/A14-channelz.md
 class ChannelTrace {
  public:
-  ChannelTrace(size_t max_event_memory);
+  explicit ChannelTrace(size_t max_event_memory);
   ~ChannelTrace();
 
   enum Severity {
diff --git a/src/core/lib/gprpp/ref_counted.h b/src/core/lib/gprpp/ref_counted.h
index bb5e18020c7..64f3f8fc9cf 100644
--- a/src/core/lib/gprpp/ref_counted.h
+++ b/src/core/lib/gprpp/ref_counted.h
@@ -221,12 +221,12 @@ class Delete;
 template <typename T>
 class Delete<T, true> {
  public:
-  Delete(T* t) { delete t; }
+  explicit Delete(T* t) { delete t; }
 };
 template <typename T>
 class Delete<T, false> {
  public:
-  Delete(T* t) {}
+  explicit Delete(T* t) {}
 };
 }  // namespace internal
 
diff --git a/src/core/lib/gprpp/ref_counted_ptr.h b/src/core/lib/gprpp/ref_counted_ptr.h
index 62fb39fa019..fd3bfbda87c 100644
--- a/src/core/lib/gprpp/ref_counted_ptr.h
+++ b/src/core/lib/gprpp/ref_counted_ptr.h
@@ -35,10 +35,12 @@ template <typename T>
 class RefCountedPtr {
  public:
   RefCountedPtr() {}
+  // NOLINTNEXTLINE(google-explicit-constructor)
   RefCountedPtr(std::nullptr_t) {}
 
   // If value is non-null, we take ownership of a ref to it.
   template <typename Y>
+  // NOLINTNEXTLINE(google-explicit-constructor)
   RefCountedPtr(Y* value) : value_(value) {}
 
   // Move ctors.
@@ -47,6 +49,7 @@ class RefCountedPtr {
     other.value_ = nullptr;
   }
   template <typename Y>
+  // NOLINTNEXTLINE(google-explicit-constructor)
   RefCountedPtr(RefCountedPtr<Y>&& other) noexcept {
     value_ = static_cast<T*>(other.value_);
     other.value_ = nullptr;
@@ -71,6 +74,7 @@ class RefCountedPtr {
     value_ = other.value_;
   }
   template <typename Y>
+  // NOLINTNEXTLINE(google-explicit-constructor)
   RefCountedPtr(const RefCountedPtr<Y>& other) {
     static_assert(std::has_virtual_destructor<T>::value,
                   "T does not have a virtual dtor");
@@ -181,11 +185,13 @@ template <typename T>
 class WeakRefCountedPtr {
  public:
   WeakRefCountedPtr() {}
+  // NOLINTNEXTLINE(google-explicit-constructor)
   WeakRefCountedPtr(std::nullptr_t) {}
 
   // If value is non-null, we take ownership of a ref to it.
   template <typename Y>
-  explicit WeakRefCountedPtr(Y* value) {
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  WeakRefCountedPtr(Y* value) {
     value_ = value;
   }
 
@@ -195,6 +201,7 @@ class WeakRefCountedPtr {
     other.value_ = nullptr;
   }
   template <typename Y>
+  // NOLINTNEXTLINE(google-explicit-constructor)
   WeakRefCountedPtr(WeakRefCountedPtr<Y>&& other) noexcept {
     value_ = static_cast<T*>(other.value_);
     other.value_ = nullptr;
@@ -219,6 +226,7 @@ class WeakRefCountedPtr {
     value_ = other.value_;
   }
   template <typename Y>
+  // NOLINTNEXTLINE(google-explicit-constructor)
   WeakRefCountedPtr(const WeakRefCountedPtr<Y>& other) {
     static_assert(std::has_virtual_destructor<T>::value,
                   "T does not have a virtual dtor");
diff --git a/src/core/lib/http/httpcli_security_connector.cc b/src/core/lib/http/httpcli_security_connector.cc
index 966a8fb6415..15aea333c77 100644
--- a/src/core/lib/http/httpcli_security_connector.cc
+++ b/src/core/lib/http/httpcli_security_connector.cc
@@ -43,7 +43,7 @@
 class grpc_httpcli_ssl_channel_security_connector final
     : public grpc_channel_security_connector {
  public:
-  grpc_httpcli_ssl_channel_security_connector(char* secure_peer_name)
+  explicit grpc_httpcli_ssl_channel_security_connector(char* secure_peer_name)
       : grpc_channel_security_connector(
             /*url_scheme=*/nullptr,
             /*channel_creds=*/nullptr,
diff --git a/src/core/lib/iomgr/exec_ctx.h b/src/core/lib/iomgr/exec_ctx.h
index 7340e36e560..c993133ef1c 100644
--- a/src/core/lib/iomgr/exec_ctx.h
+++ b/src/core/lib/iomgr/exec_ctx.h
@@ -113,7 +113,7 @@ class ExecCtx {
   }
 
   /** Parameterised Constructor */
-  ExecCtx(uintptr_t fl) : flags_(fl) {
+  explicit ExecCtx(uintptr_t fl) : flags_(fl) {
     if (!(GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
       grpc_core::Fork::IncExecCtxCount();
     }
@@ -308,7 +308,9 @@ class ApplicationCallbackExecCtx {
   ApplicationCallbackExecCtx() { Set(this, flags_); }
 
   /** Parameterised Constructor */
-  ApplicationCallbackExecCtx(uintptr_t fl) : flags_(fl) { Set(this, flags_); }
+  explicit ApplicationCallbackExecCtx(uintptr_t fl) : flags_(fl) {
+    Set(this, flags_);
+  }
 
   ~ApplicationCallbackExecCtx() {
     if (reinterpret_cast<ApplicationCallbackExecCtx*>(
diff --git a/src/core/lib/iomgr/executor.h b/src/core/lib/iomgr/executor.h
index 71337004841..7a5d16b9fc5 100644
--- a/src/core/lib/iomgr/executor.h
+++ b/src/core/lib/iomgr/executor.h
@@ -54,7 +54,7 @@ enum class ExecutorJobType {
 
 class Executor {
  public:
-  Executor(const char* executor_name);
+  explicit Executor(const char* executor_name);
 
   void Init();
 
diff --git a/src/core/lib/iomgr/executor/threadpool.h b/src/core/lib/iomgr/executor/threadpool.h
index 5f8a9680aa3..66218b52b62 100644
--- a/src/core/lib/iomgr/executor/threadpool.h
+++ b/src/core/lib/iomgr/executor/threadpool.h
@@ -99,7 +99,7 @@ class ThreadPool : public ThreadPoolInterface {
   // Creates a thread pool with size of "num_threads", with default thread name
   // "ThreadPoolWorker" and all thread options set to default. If the given size
   // is 0 or less, there will be 1 worker thread created inside pool.
-  ThreadPool(int num_threads);
+  explicit ThreadPool(int num_threads);
 
   // Same as ThreadPool(int num_threads) constructor, except
   // that it also sets "thd_name" as the name of all threads in the thread pool.
diff --git a/src/core/lib/iomgr/poller/eventmanager_libuv.h b/src/core/lib/iomgr/poller/eventmanager_libuv.h
index 3c0e05d394e..0bd0ecc4161 100644
--- a/src/core/lib/iomgr/poller/eventmanager_libuv.h
+++ b/src/core/lib/iomgr/poller/eventmanager_libuv.h
@@ -36,7 +36,7 @@ class LibuvEventManager {
   class Options {
    public:
     Options();
-    Options(int num_workers);
+    explicit Options(int num_workers);
 
     int num_workers() const { return num_workers_; }
     void set_num_workers(int num) { num_workers_ = num; }
diff --git a/src/core/lib/iomgr/tcp_posix.cc b/src/core/lib/iomgr/tcp_posix.cc
index d33e9ef12c0..7813e044c50 100644
--- a/src/core/lib/iomgr/tcp_posix.cc
+++ b/src/core/lib/iomgr/tcp_posix.cc
@@ -181,8 +181,9 @@ class TcpZerocopySendCtx {
   static constexpr int kDefaultMaxSends = 4;
   static constexpr size_t kDefaultSendBytesThreshold = 16 * 1024;  // 16KB
 
-  TcpZerocopySendCtx(int max_sends = kDefaultMaxSends,
-                     size_t send_bytes_threshold = kDefaultSendBytesThreshold)
+  explicit TcpZerocopySendCtx(
+      int max_sends = kDefaultMaxSends,
+      size_t send_bytes_threshold = kDefaultSendBytesThreshold)
       : max_sends_(max_sends),
         free_send_records_size_(max_sends),
         threshold_bytes_(send_bytes_threshold) {
diff --git a/src/core/lib/json/json.h b/src/core/lib/json/json.h
index 4916fe2a849..9b3e0be7bfd 100644
--- a/src/core/lib/json/json.h
+++ b/src/core/lib/json/json.h
@@ -76,6 +76,7 @@ class Json {
 
   // Construct from copying a string.
   // If is_number is true, the type will be NUMBER instead of STRING.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(const std::string& string, bool is_number = false)
       : type_(is_number ? Type::NUMBER : Type::STRING), string_value_(string) {}
   Json& operator=(const std::string& string) {
@@ -85,12 +86,14 @@ class Json {
   }
 
   // Same thing for C-style strings, both const and mutable.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(const char* string, bool is_number = false)
       : Json(std::string(string), is_number) {}
   Json& operator=(const char* string) {
     *this = std::string(string);
     return *this;
   }
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(char* string, bool is_number = false)
       : Json(std::string(string), is_number) {}
   Json& operator=(char* string) {
@@ -99,6 +102,7 @@ class Json {
   }
 
   // Construct by moving a string.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(std::string&& string)
       : type_(Type::STRING), string_value_(std::move(string)) {}
   Json& operator=(std::string&& string) {
@@ -108,6 +112,7 @@ class Json {
   }
 
   // Construct from bool.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(bool b) : type_(b ? Type::JSON_TRUE : Type::JSON_FALSE) {}
   Json& operator=(bool b) {
     type_ = b ? Type::JSON_TRUE : Type::JSON_FALSE;
@@ -116,6 +121,7 @@ class Json {
 
   // Construct from any numeric type.
   template <typename NumericType>
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(NumericType number)
       : type_(Type::NUMBER), string_value_(std::to_string(number)) {}
   template <typename NumericType>
@@ -126,6 +132,7 @@ class Json {
   }
 
   // Construct by copying object.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(const Object& object) : type_(Type::OBJECT), object_value_(object) {}
   Json& operator=(const Object& object) {
     type_ = Type::OBJECT;
@@ -134,6 +141,7 @@ class Json {
   }
 
   // Construct by moving object.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(Object&& object)
       : type_(Type::OBJECT), object_value_(std::move(object)) {}
   Json& operator=(Object&& object) {
@@ -143,6 +151,7 @@ class Json {
   }
 
   // Construct by copying array.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(const Array& array) : type_(Type::ARRAY), array_value_(array) {}
   Json& operator=(const Array& array) {
     type_ = Type::ARRAY;
@@ -151,6 +160,7 @@ class Json {
   }
 
   // Construct by moving array.
+  // NOLINTNEXTLINE(google-explicit-constructor)
   Json(Array&& array) : type_(Type::ARRAY), array_value_(std::move(array)) {}
   Json& operator=(Array&& array) {
     type_ = Type::ARRAY;
diff --git a/src/core/lib/security/credentials/oauth2/oauth2_credentials.h b/src/core/lib/security/credentials/oauth2/oauth2_credentials.h
index 2a9b37e1fec..6111d9adcaa 100644
--- a/src/core/lib/security/credentials/oauth2/oauth2_credentials.h
+++ b/src/core/lib/security/credentials/oauth2/oauth2_credentials.h
@@ -107,7 +107,8 @@ class grpc_oauth2_token_fetcher_credentials : public grpc_call_credentials {
 class grpc_google_refresh_token_credentials final
     : public grpc_oauth2_token_fetcher_credentials {
  public:
-  grpc_google_refresh_token_credentials(grpc_auth_refresh_token refresh_token);
+  explicit grpc_google_refresh_token_credentials(
+      grpc_auth_refresh_token refresh_token);
   ~grpc_google_refresh_token_credentials() override;
 
   const grpc_auth_refresh_token& refresh_token() const {
@@ -130,7 +131,7 @@ class grpc_google_refresh_token_credentials final
 // Access token credentials.
 class grpc_access_token_credentials final : public grpc_call_credentials {
  public:
-  grpc_access_token_credentials(const char* access_token);
+  explicit grpc_access_token_credentials(const char* access_token);
   ~grpc_access_token_credentials() override;
 
   bool get_request_metadata(grpc_polling_entity* pollent,
diff --git a/src/core/lib/security/credentials/ssl/ssl_credentials.h b/src/core/lib/security/credentials/ssl/ssl_credentials.h
index 4c90813f8d2..0c5af81c7d8 100644
--- a/src/core/lib/security/credentials/ssl/ssl_credentials.h
+++ b/src/core/lib/security/credentials/ssl/ssl_credentials.h
@@ -64,7 +64,7 @@ struct grpc_ssl_server_certificate_config_fetcher {
 
 class grpc_ssl_server_credentials final : public grpc_server_credentials {
  public:
-  grpc_ssl_server_credentials(
+  explicit grpc_ssl_server_credentials(
       const grpc_ssl_server_credentials_options& options);
   ~grpc_ssl_server_credentials() override;
 
diff --git a/src/core/lib/security/security_connector/alts/alts_security_connector.cc b/src/core/lib/security/security_connector/alts/alts_security_connector.cc
index 47c357f8fab..64c39e6d5e3 100644
--- a/src/core/lib/security/security_connector/alts/alts_security_connector.cc
+++ b/src/core/lib/security/security_connector/alts/alts_security_connector.cc
@@ -134,7 +134,7 @@ class grpc_alts_channel_security_connector final
 class grpc_alts_server_security_connector final
     : public grpc_server_security_connector {
  public:
-  grpc_alts_server_security_connector(
+  explicit grpc_alts_server_security_connector(
       grpc_core::RefCountedPtr<grpc_server_credentials> server_creds)
       : grpc_server_security_connector(GRPC_ALTS_URL_SCHEME,
                                        std::move(server_creds)) {}
diff --git a/src/core/lib/security/security_connector/fake/fake_security_connector.cc b/src/core/lib/security/security_connector/fake/fake_security_connector.cc
index 0e3b1e8b973..fdf750f4ede 100644
--- a/src/core/lib/security/security_connector/fake/fake_security_connector.cc
+++ b/src/core/lib/security/security_connector/fake/fake_security_connector.cc
@@ -275,7 +275,7 @@ void grpc_fake_channel_security_connector::check_peer(
 class grpc_fake_server_security_connector
     : public grpc_server_security_connector {
  public:
-  grpc_fake_server_security_connector(
+  explicit grpc_fake_server_security_connector(
       grpc_core::RefCountedPtr<grpc_server_credentials> server_creds)
       : grpc_server_security_connector(GRPC_FAKE_SECURITY_URL_SCHEME,
                                        std::move(server_creds)) {}
diff --git a/src/core/lib/security/security_connector/insecure/insecure_security_connector.h b/src/core/lib/security/security_connector/insecure/insecure_security_connector.h
index f55ae02bd67..7d0f79e90f1 100644
--- a/src/core/lib/security/security_connector/insecure/insecure_security_connector.h
+++ b/src/core/lib/security/security_connector/insecure/insecure_security_connector.h
@@ -65,7 +65,7 @@ class InsecureChannelSecurityConnector
 
 class InsecureServerSecurityConnector : public grpc_server_security_connector {
  public:
-  InsecureServerSecurityConnector(
+  explicit InsecureServerSecurityConnector(
       grpc_core::RefCountedPtr<grpc_server_credentials> server_creds)
       : grpc_server_security_connector(nullptr /* url_scheme */,
                                        std::move(server_creds)) {}
diff --git a/src/core/lib/security/security_connector/local/local_security_connector.cc b/src/core/lib/security/security_connector/local/local_security_connector.cc
index 3313fd01247..2cec0dbb9a5 100644
--- a/src/core/lib/security/security_connector/local/local_security_connector.cc
+++ b/src/core/lib/security/security_connector/local/local_security_connector.cc
@@ -206,7 +206,7 @@ class grpc_local_channel_security_connector final
 class grpc_local_server_security_connector final
     : public grpc_server_security_connector {
  public:
-  grpc_local_server_security_connector(
+  explicit grpc_local_server_security_connector(
       grpc_core::RefCountedPtr<grpc_server_credentials> server_creds)
       : grpc_server_security_connector(nullptr, std::move(server_creds)) {}
   ~grpc_local_server_security_connector() override = default;
diff --git a/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc b/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc
index 41a2252435c..ee5672b955a 100644
--- a/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc
+++ b/src/core/lib/security/security_connector/ssl/ssl_security_connector.cc
@@ -206,7 +206,7 @@ class grpc_ssl_channel_security_connector final
 class grpc_ssl_server_security_connector
     : public grpc_server_security_connector {
  public:
-  grpc_ssl_server_security_connector(
+  explicit grpc_ssl_server_security_connector(
       grpc_core::RefCountedPtr<grpc_server_credentials> server_creds)
       : grpc_server_security_connector(GRPC_SSL_URL_SCHEME,
                                        std::move(server_creds)) {}
diff --git a/src/core/lib/slice/slice_internal.h b/src/core/lib/slice/slice_internal.h
index 6ada6b0f945..1cbe32baf6b 100644
--- a/src/core/lib/slice/slice_internal.h
+++ b/src/core/lib/slice/slice_internal.h
@@ -176,7 +176,7 @@ namespace grpc_core {
 struct StaticSliceRefcount {
   static grpc_slice_refcount kStaticSubRefcount;
 
-  StaticSliceRefcount(uint32_t index)
+  explicit StaticSliceRefcount(uint32_t index)
       : base(&kStaticSubRefcount, grpc_slice_refcount::Type::STATIC),
         index(index) {}
 
diff --git a/src/core/lib/surface/call.cc b/src/core/lib/surface/call.cc
index 3e9db709ada..d749d396eda 100644
--- a/src/core/lib/surface/call.cc
+++ b/src/core/lib/surface/call.cc
@@ -124,7 +124,7 @@ struct parent_call {
 };
 
 struct child_call {
-  child_call(grpc_call* parent) : parent(parent) {}
+  explicit child_call(grpc_call* parent) : parent(parent) {}
   grpc_call* parent;
   /** siblings: children of the same parent form a list, and this list is
      protected under
diff --git a/src/core/lib/surface/completion_queue.cc b/src/core/lib/surface/completion_queue.cc
index c262cc95978..02ac5067a31 100644
--- a/src/core/lib/surface/completion_queue.cc
+++ b/src/core/lib/surface/completion_queue.cc
@@ -310,7 +310,7 @@ struct cq_pluck_data {
 };
 
 struct cq_callback_data {
-  cq_callback_data(
+  explicit cq_callback_data(
       grpc_experimental_completion_queue_functor* shutdown_callback)
       : shutdown_callback(shutdown_callback) {}
 
@@ -913,7 +913,8 @@ struct cq_is_finished_arg {
 };
 class ExecCtxNext : public grpc_core::ExecCtx {
  public:
-  ExecCtxNext(void* arg) : ExecCtx(0), check_ready_to_finish_arg_(arg) {}
+  explicit ExecCtxNext(void* arg)
+      : ExecCtx(0), check_ready_to_finish_arg_(arg) {}
 
   bool CheckReadyToFinish() override {
     cq_is_finished_arg* a =
@@ -1161,7 +1162,8 @@ static void del_plucker(grpc_completion_queue* cq, void* tag,
 
 class ExecCtxPluck : public grpc_core::ExecCtx {
  public:
-  ExecCtxPluck(void* arg) : ExecCtx(0), check_ready_to_finish_arg_(arg) {}
+  explicit ExecCtxPluck(void* arg)
+      : ExecCtx(0), check_ready_to_finish_arg_(arg) {}
 
   bool CheckReadyToFinish() override {
     cq_is_finished_arg* a =
diff --git a/src/core/lib/transport/connectivity_state.h b/src/core/lib/transport/connectivity_state.h
index cad34c27003..e5fee88e3b7 100644
--- a/src/core/lib/transport/connectivity_state.h
+++ b/src/core/lib/transport/connectivity_state.h
@@ -95,9 +95,9 @@ class AsyncConnectivityStateWatcherInterface
 // to be called).
 class ConnectivityStateTracker {
  public:
-  ConnectivityStateTracker(const char* name,
-                           grpc_connectivity_state state = GRPC_CHANNEL_IDLE,
-                           const absl::Status& status = absl::Status())
+  explicit ConnectivityStateTracker(
+      const char* name, grpc_connectivity_state state = GRPC_CHANNEL_IDLE,
+      const absl::Status& status = absl::Status())
       : name_(name), state_(state), status_(status) {}
 
   ~ConnectivityStateTracker();
diff --git a/src/core/tsi/ssl/session_cache/ssl_session_boringssl.cc b/src/core/tsi/ssl/session_cache/ssl_session_boringssl.cc
index 612ecfffd46..dcfff00cb9a 100644
--- a/src/core/tsi/ssl/session_cache/ssl_session_boringssl.cc
+++ b/src/core/tsi/ssl/session_cache/ssl_session_boringssl.cc
@@ -32,7 +32,7 @@ namespace {
 
 class BoringSslCachedSession : public SslCachedSession {
  public:
-  BoringSslCachedSession(SslSessionPtr session)
+  explicit BoringSslCachedSession(SslSessionPtr session)
       : session_(std::move(session)) {}
 
   SslSessionPtr CopySession() const override {
diff --git a/src/cpp/server/dynamic_thread_pool.h b/src/cpp/server/dynamic_thread_pool.h
index 3bc7b677bad..954aaff35da 100644
--- a/src/cpp/server/dynamic_thread_pool.h
+++ b/src/cpp/server/dynamic_thread_pool.h
@@ -41,7 +41,7 @@ class DynamicThreadPool final : public ThreadPoolInterface {
  private:
   class DynamicThread {
    public:
-    DynamicThread(DynamicThreadPool* pool);
+    explicit DynamicThread(DynamicThreadPool* pool);
     ~DynamicThread();
 
    private:
diff --git a/src/cpp/server/secure_server_credentials.h b/src/cpp/server/secure_server_credentials.h
index 4e24b2534da..730abdb83cd 100644
--- a/src/cpp/server/secure_server_credentials.h
+++ b/src/cpp/server/secure_server_credentials.h
@@ -40,7 +40,7 @@ class AuthMetadataProcessorAyncWrapper final {
                       const grpc_metadata* md, size_t num_md,
                       grpc_process_auth_metadata_done_cb cb, void* user_data);
 
-  AuthMetadataProcessorAyncWrapper(
+  explicit AuthMetadataProcessorAyncWrapper(
       const std::shared_ptr<AuthMetadataProcessor>& processor)
       : processor_(processor) {
     if (processor && processor->IsBlocking()) {
diff --git a/src/cpp/server/server_cc.cc b/src/cpp/server/server_cc.cc
index 933ef938efa..13357ae4919 100644
--- a/src/cpp/server/server_cc.cc
+++ b/src/cpp/server/server_cc.cc
@@ -315,7 +315,7 @@ class Server::UnimplementedAsyncResponse final
           grpc::internal::CallOpSendInitialMetadata,
           grpc::internal::CallOpServerSendStatus> {
  public:
-  UnimplementedAsyncResponse(UnimplementedAsyncRequest* request);
+  explicit UnimplementedAsyncResponse(UnimplementedAsyncRequest* request);
   ~UnimplementedAsyncResponse() override { delete request_; }
 
   bool FinalizeResult(void** tag, bool* status) override {
@@ -592,7 +592,7 @@ class Server::CallbackRequest final
 
   class CallbackCallTag : public grpc_experimental_completion_queue_functor {
    public:
-    CallbackCallTag(Server::CallbackRequest<ServerContextType>* req)
+    explicit CallbackCallTag(Server::CallbackRequest<ServerContextType>* req)
         : req_(req) {
       functor_run = &CallbackCallTag::StaticRun;
       // Set inlineable to true since this callback is internally-controlled
diff --git a/src/cpp/thread_manager/thread_manager.h b/src/cpp/thread_manager/thread_manager.h
index 43f1fd5585f..aae24177873 100644
--- a/src/cpp/thread_manager/thread_manager.h
+++ b/src/cpp/thread_manager/thread_manager.h
@@ -119,7 +119,7 @@ class ThreadManager {
   // not be called (and the need for this WorkerThread class is eliminated)
   class WorkerThread {
    public:
-    WorkerThread(ThreadManager* thd_mgr);
+    explicit WorkerThread(ThreadManager* thd_mgr);
     ~WorkerThread();
 
     bool created() const { return created_; }
diff --git a/test/core/channel/channel_trace_test.cc b/test/core/channel/channel_trace_test.cc
index f0917fa67fa..0ecefede9c3 100644
--- a/test/core/channel/channel_trace_test.cc
+++ b/test/core/channel/channel_trace_test.cc
@@ -102,7 +102,7 @@ void ValidateChannelTrace(ChannelTrace* tracer, size_t num_events_logged) {
 
 class ChannelFixture {
  public:
-  ChannelFixture(int max_tracer_event_memory) {
+  explicit ChannelFixture(int max_tracer_event_memory) {
     grpc_arg client_a = grpc_channel_arg_integer_create(
         const_cast<char*>(GRPC_ARG_MAX_CHANNEL_TRACE_EVENT_MEMORY_PER_NODE),
         max_tracer_event_memory);
diff --git a/test/core/channel/channelz_test.cc b/test/core/channel/channelz_test.cc
index 3c7c89848e0..0da9f6f9339 100644
--- a/test/core/channel/channelz_test.cc
+++ b/test/core/channel/channelz_test.cc
@@ -143,7 +143,7 @@ void ValidateGetServers(size_t expected_servers) {
 
 class ChannelFixture {
  public:
-  ChannelFixture(int max_tracer_event_memory = 0) {
+  explicit ChannelFixture(int max_tracer_event_memory = 0) {
     grpc_arg client_a[] = {
         grpc_channel_arg_integer_create(
             const_cast<char*>(GRPC_ARG_MAX_CHANNEL_TRACE_EVENT_MEMORY_PER_NODE),
diff --git a/test/core/client_channel/service_config_test.cc b/test/core/client_channel/service_config_test.cc
index 97749cfb15f..6df340f5b47 100644
--- a/test/core/client_channel/service_config_test.cc
+++ b/test/core/client_channel/service_config_test.cc
@@ -38,7 +38,7 @@ namespace testing {
 
 class TestParsedConfig1 : public ServiceConfigParser::ParsedConfig {
  public:
-  TestParsedConfig1(int value) : value_(value) {}
+  explicit TestParsedConfig1(int value) : value_(value) {}
 
   int value() const { return value_; }
 
diff --git a/test/core/iomgr/mpmcqueue_test.cc b/test/core/iomgr/mpmcqueue_test.cc
index 93beb663b01..d63ae7893c2 100644
--- a/test/core/iomgr/mpmcqueue_test.cc
+++ b/test/core/iomgr/mpmcqueue_test.cc
@@ -30,7 +30,7 @@ struct WorkItem {
   int index;
   bool done;
 
-  WorkItem(int i) : index(i) { done = false; }
+  explicit WorkItem(int i) : index(i) { done = false; }
 };
 
 // Thread to "produce" items and put items into queue
@@ -77,7 +77,7 @@ class ProducerThread {
 // Thread to pull out items from queue
 class ConsumerThread {
  public:
-  ConsumerThread(grpc_core::InfLenFIFOQueue* queue) : queue_(queue) {
+  explicit ConsumerThread(grpc_core::InfLenFIFOQueue* queue) : queue_(queue) {
     thd_ = grpc_core::Thread(
         "mpmcq_test_consumer_thd",
         [](void* th) { static_cast<ConsumerThread*>(th)->Run(); }, this);
diff --git a/test/core/iomgr/poller/eventmanager_libuv_test.cc b/test/core/iomgr/poller/eventmanager_libuv_test.cc
index 8443e9f4c02..82b6de1b913 100644
--- a/test/core/iomgr/poller/eventmanager_libuv_test.cc
+++ b/test/core/iomgr/poller/eventmanager_libuv_test.cc
@@ -32,7 +32,8 @@ namespace {
 
 TEST(LibuvEventManager, Allocation) {
   for (int i = 0; i < 10; i++) {
-    LibuvEventManager* em = new LibuvEventManager(i);
+    LibuvEventManager* em =
+        new LibuvEventManager(LibuvEventManager::Options(i));
     gpr_sleep_until(grpc_timeout_milliseconds_to_deadline(1));
     delete em;
   }
@@ -40,7 +41,8 @@ TEST(LibuvEventManager, Allocation) {
 
 TEST(LibuvEventManager, ShutdownRef) {
   for (int i = 0; i < 10; i++) {
-    LibuvEventManager* em = new LibuvEventManager(i);
+    LibuvEventManager* em =
+        new LibuvEventManager(LibuvEventManager::Options(i));
     for (int j = 0; j < i; j++) {
       em->ShutdownRef();
     }
@@ -54,7 +56,8 @@ TEST(LibuvEventManager, ShutdownRef) {
 
 TEST(LibuvEventManager, ShutdownRefAsync) {
   for (int i = 0; i < 10; i++) {
-    LibuvEventManager* em = new LibuvEventManager(i);
+    LibuvEventManager* em =
+        new LibuvEventManager(LibuvEventManager::Options(i));
     for (int j = 0; j < i; j++) {
       em->ShutdownRef();
     }
diff --git a/test/core/surface/completion_queue_test.cc b/test/core/surface/completion_queue_test.cc
index 22079f88ae8..cbf536fa16c 100644
--- a/test/core/surface/completion_queue_test.cc
+++ b/test/core/surface/completion_queue_test.cc
@@ -380,7 +380,7 @@ static void test_callback(void) {
   bool got_shutdown = false;
   class ShutdownCallback : public grpc_experimental_completion_queue_functor {
    public:
-    ShutdownCallback(bool* done) : done_(done) {
+    explicit ShutdownCallback(bool* done) : done_(done) {
       functor_run = &ShutdownCallback::Run;
       inlineable = false;
     }
diff --git a/test/core/tsi/alts/handshaker/alts_concurrent_connectivity_test.cc b/test/core/tsi/alts/handshaker/alts_concurrent_connectivity_test.cc
index c96a6141f43..bc2eca1a61b 100644
--- a/test/core/tsi/alts/handshaker/alts_concurrent_connectivity_test.cc
+++ b/test/core/tsi/alts/handshaker/alts_concurrent_connectivity_test.cc
@@ -104,7 +104,7 @@ grpc_channel* create_secure_channel_for_test(
 
 class FakeHandshakeServer {
  public:
-  FakeHandshakeServer(bool check_num_concurrent_rpcs) {
+  explicit FakeHandshakeServer(bool check_num_concurrent_rpcs) {
     int port = grpc_pick_unused_port_or_die();
     address_ = grpc_core::JoinHostPort("localhost", port);
     if (check_num_concurrent_rpcs) {
diff --git a/test/core/xds/xds_bootstrap_test.cc b/test/core/xds/xds_bootstrap_test.cc
index 7a7545dca1d..d74bbf035a6 100644
--- a/test/core/xds/xds_bootstrap_test.cc
+++ b/test/core/xds/xds_bootstrap_test.cc
@@ -36,7 +36,7 @@ namespace testing {
 
 class TestType {
  public:
-  TestType(bool parse_xds_certificate_providers)
+  explicit TestType(bool parse_xds_certificate_providers)
       : parse_xds_certificate_providers_(parse_xds_certificate_providers) {}
 
   bool parse_xds_certificate_providers() const {
diff --git a/test/cpp/end2end/client_callback_end2end_test.cc b/test/cpp/end2end/client_callback_end2end_test.cc
index bc093534944..e38bd7115cc 100644
--- a/test/cpp/end2end/client_callback_end2end_test.cc
+++ b/test/cpp/end2end/client_callback_end2end_test.cc
@@ -806,7 +806,7 @@ TEST_P(ClientCallbackEnd2endTest, UnaryReactor) {
   ResetStub();
   class UnaryClient : public grpc::experimental::ClientUnaryReactor {
    public:
-    UnaryClient(grpc::testing::EchoTestService::Stub* stub) {
+    explicit UnaryClient(grpc::testing::EchoTestService::Stub* stub) {
       cli_ctx_.AddMetadata("key1", "val1");
       cli_ctx_.AddMetadata("key2", "val2");
       request_.mutable_param()->set_echo_metadata_initially(true);
@@ -1351,7 +1351,7 @@ TEST_P(ClientCallbackEnd2endTest, SimultaneousReadAndWritesDone) {
   class Client : public grpc::experimental::ClientBidiReactor<EchoRequest,
                                                               EchoResponse> {
    public:
-    Client(grpc::testing::EchoTestService::Stub* stub) {
+    explicit Client(grpc::testing::EchoTestService::Stub* stub) {
       request_.set_message("Hello bidi ");
       stub->experimental_async()->BidiStream(&context_, this);
       StartWrite(&request_);
@@ -1434,7 +1434,8 @@ TEST_P(ClientCallbackEnd2endTest,
   class ReadAllIncomingDataClient
       : public grpc::experimental::ClientReadReactor<EchoResponse> {
    public:
-    ReadAllIncomingDataClient(grpc::testing::EchoTestService::Stub* stub) {
+    explicit ReadAllIncomingDataClient(
+        grpc::testing::EchoTestService::Stub* stub) {
       request_.set_message("Hello client ");
       stub->experimental_async()->ResponseStream(&context_, &request_, this);
     }
diff --git a/test/cpp/end2end/client_interceptors_end2end_test.cc b/test/cpp/end2end/client_interceptors_end2end_test.cc
index 8bc81bfb361..af454198eb2 100644
--- a/test/cpp/end2end/client_interceptors_end2end_test.cc
+++ b/test/cpp/end2end/client_interceptors_end2end_test.cc
@@ -72,7 +72,7 @@ enum class ChannelType {
 /* Hijacks Echo RPC and fills in the expected values */
 class HijackingInterceptor : public experimental::Interceptor {
  public:
-  HijackingInterceptor(experimental::ClientRpcInfo* info) {
+  explicit HijackingInterceptor(experimental::ClientRpcInfo* info) {
     info_ = info;
     // Make sure it is the right method
     EXPECT_EQ(strcmp("/grpc.testing.EchoTestService/Echo", info->method()), 0);
@@ -178,7 +178,8 @@ class HijackingInterceptorFactory
 
 class HijackingInterceptorMakesAnotherCall : public experimental::Interceptor {
  public:
-  HijackingInterceptorMakesAnotherCall(experimental::ClientRpcInfo* info) {
+  explicit HijackingInterceptorMakesAnotherCall(
+      experimental::ClientRpcInfo* info) {
     info_ = info;
     // Make sure it is the right method
     EXPECT_EQ(strcmp("/grpc.testing.EchoTestService/Echo", info->method()), 0);
@@ -300,7 +301,8 @@ class HijackingInterceptorMakesAnotherCallFactory
 
 class BidiStreamingRpcHijackingInterceptor : public experimental::Interceptor {
  public:
-  BidiStreamingRpcHijackingInterceptor(experimental::ClientRpcInfo* info) {
+  explicit BidiStreamingRpcHijackingInterceptor(
+      experimental::ClientRpcInfo* info) {
     info_ = info;
   }
 
@@ -370,7 +372,8 @@ class BidiStreamingRpcHijackingInterceptor : public experimental::Interceptor {
 class ClientStreamingRpcHijackingInterceptor
     : public experimental::Interceptor {
  public:
-  ClientStreamingRpcHijackingInterceptor(experimental::ClientRpcInfo* info) {
+  explicit ClientStreamingRpcHijackingInterceptor(
+      experimental::ClientRpcInfo* info) {
     info_ = info;
   }
   void Intercept(experimental::InterceptorBatchMethods* methods) override {
@@ -424,7 +427,8 @@ class ClientStreamingRpcHijackingInterceptorFactory
 class ServerStreamingRpcHijackingInterceptor
     : public experimental::Interceptor {
  public:
-  ServerStreamingRpcHijackingInterceptor(experimental::ClientRpcInfo* info) {
+  explicit ServerStreamingRpcHijackingInterceptor(
+      experimental::ClientRpcInfo* info) {
     info_ = info;
     got_failed_message_ = false;
   }
@@ -534,7 +538,7 @@ class BidiStreamingRpcHijackingInterceptorFactory
 // single RPC should be made on the channel before calling the Verify methods.
 class LoggingInterceptor : public experimental::Interceptor {
  public:
-  LoggingInterceptor(experimental::ClientRpcInfo* /*info*/) {
+  explicit LoggingInterceptor(experimental::ClientRpcInfo* /*info*/) {
     pre_send_initial_metadata_ = false;
     pre_send_message_count_ = 0;
     pre_send_close_ = false;
diff --git a/test/cpp/end2end/delegating_channel_test.cc b/test/cpp/end2end/delegating_channel_test.cc
index 9b371e29a29..5ff66d8ffd1 100644
--- a/test/cpp/end2end/delegating_channel_test.cc
+++ b/test/cpp/end2end/delegating_channel_test.cc
@@ -45,7 +45,8 @@ namespace {
 
 class TestChannel : public experimental::DelegatingChannel {
  public:
-  TestChannel(const std::shared_ptr<ChannelInterface>& delegate_channel)
+  explicit TestChannel(
+      const std::shared_ptr<ChannelInterface>& delegate_channel)
       : experimental::DelegatingChannel(delegate_channel) {}
   // Always returns GRPC_CHANNEL_READY
   grpc_connectivity_state GetState(bool /*try_to_connect*/) override {
diff --git a/test/cpp/end2end/end2end_test.cc b/test/cpp/end2end/end2end_test.cc
index 08e75eff61f..906d0fa5160 100644
--- a/test/cpp/end2end/end2end_test.cc
+++ b/test/cpp/end2end/end2end_test.cc
@@ -204,7 +204,8 @@ class TestAuthMetadataProcessor : public AuthMetadataProcessor {
  public:
   static const char kGoodGuy[];
 
-  TestAuthMetadataProcessor(bool is_blocking) : is_blocking_(is_blocking) {}
+  explicit TestAuthMetadataProcessor(bool is_blocking)
+      : is_blocking_(is_blocking) {}
 
   std::shared_ptr<CallCredentials> GetCompatibleClientCreds() {
     return grpc::MetadataCredentialsFromPlugin(
@@ -259,7 +260,7 @@ const char TestAuthMetadataProcessor::kIdentityPropName[] = "novel identity";
 
 class Proxy : public ::grpc::testing::EchoTestService::Service {
  public:
-  Proxy(const std::shared_ptr<Channel>& channel)
+  explicit Proxy(const std::shared_ptr<Channel>& channel)
       : stub_(grpc::testing::EchoTestService::NewStub(channel)) {}
 
   Status Echo(ServerContext* server_context, const EchoRequest* request,
@@ -1857,7 +1858,8 @@ TEST_P(SecureEnd2endTest, SetPerCallCredentials) {
 
 class CredentialsInterceptor : public experimental::Interceptor {
  public:
-  CredentialsInterceptor(experimental::ClientRpcInfo* info) : info_(info) {}
+  explicit CredentialsInterceptor(experimental::ClientRpcInfo* info)
+      : info_(info) {}
 
   void Intercept(experimental::InterceptorBatchMethods* methods) override {
     if (methods->QueryInterceptionHookPoint(
diff --git a/test/cpp/end2end/server_interceptors_end2end_test.cc b/test/cpp/end2end/server_interceptors_end2end_test.cc
index 4c90514c532..43457343c65 100644
--- a/test/cpp/end2end/server_interceptors_end2end_test.cc
+++ b/test/cpp/end2end/server_interceptors_end2end_test.cc
@@ -47,7 +47,7 @@ namespace {
 
 class LoggingInterceptor : public experimental::Interceptor {
  public:
-  LoggingInterceptor(experimental::ServerRpcInfo* info) {
+  explicit LoggingInterceptor(experimental::ServerRpcInfo* info) {
     info_ = info;
 
     // Check the method name and compare to the type
@@ -150,7 +150,7 @@ class LoggingInterceptorFactory
 // Test if SendMessage function family works as expected for sync/callback apis
 class SyncSendMessageTester : public experimental::Interceptor {
  public:
-  SyncSendMessageTester(experimental::ServerRpcInfo* /*info*/) {}
+  explicit SyncSendMessageTester(experimental::ServerRpcInfo* /*info*/) {}
 
   void Intercept(experimental::InterceptorBatchMethods* methods) override {
     if (methods->QueryInterceptionHookPoint(
@@ -180,7 +180,7 @@ class SyncSendMessageTesterFactory
 // Test if SendMessage function family works as expected for sync/callback apis
 class SyncSendMessageVerifier : public experimental::Interceptor {
  public:
-  SyncSendMessageVerifier(experimental::ServerRpcInfo* /*info*/) {}
+  explicit SyncSendMessageVerifier(experimental::ServerRpcInfo* /*info*/) {}
 
   void Intercept(experimental::InterceptorBatchMethods* methods) override {
     if (methods->QueryInterceptionHookPoint(
diff --git a/test/cpp/end2end/xds_end2end_test.cc b/test/cpp/end2end/xds_end2end_test.cc
index 514b8852b0c..70c2891d195 100644
--- a/test/cpp/end2end/xds_end2end_test.cc
+++ b/test/cpp/end2end/xds_end2end_test.cc
@@ -358,7 +358,7 @@ class ClientStats {
 
     // Converts from proto message class.
     template <class UpstreamLocalityStats>
-    LocalityStats(const UpstreamLocalityStats& upstream_locality_stats)
+    explicit LocalityStats(const UpstreamLocalityStats& upstream_locality_stats)
         : total_successful_requests(
               upstream_locality_stats.total_successful_requests()),
           total_requests_in_progress(
diff --git a/test/cpp/interop/client_helper.h b/test/cpp/interop/client_helper.h
index adb9d72af56..2902ab7913f 100644
--- a/test/cpp/interop/client_helper.h
+++ b/test/cpp/interop/client_helper.h
@@ -47,7 +47,7 @@ std::shared_ptr<Channel> CreateChannelForTestCase(
 
 class InteropClientContextInspector {
  public:
-  InteropClientContextInspector(const ::grpc::ClientContext& context)
+  explicit InteropClientContextInspector(const ::grpc::ClientContext& context)
       : context_(context) {}
 
   // Inspector methods, able to peek inside ClientContext, follow.
@@ -68,7 +68,7 @@ class InteropClientContextInspector {
 
 class AdditionalMetadataInterceptor : public experimental::Interceptor {
  public:
-  AdditionalMetadataInterceptor(
+  explicit AdditionalMetadataInterceptor(
       std::multimap<std::string, std::string> additional_metadata)
       : additional_metadata_(std::move(additional_metadata)) {}
 
@@ -91,7 +91,7 @@ class AdditionalMetadataInterceptor : public experimental::Interceptor {
 class AdditionalMetadataInterceptorFactory
     : public experimental::ClientInterceptorFactoryInterface {
  public:
-  AdditionalMetadataInterceptorFactory(
+  explicit AdditionalMetadataInterceptorFactory(
       std::multimap<std::string, std::string> additional_metadata)
       : additional_metadata_(std::move(additional_metadata)) {}
 
diff --git a/test/cpp/interop/http2_client.h b/test/cpp/interop/http2_client.h
index 269d3b32e27..42728fc52e0 100644
--- a/test/cpp/interop/http2_client.h
+++ b/test/cpp/interop/http2_client.h
@@ -44,7 +44,7 @@ class Http2Client {
  private:
   class ServiceStub {
    public:
-    ServiceStub(const std::shared_ptr<Channel>& channel);
+    explicit ServiceStub(const std::shared_ptr<Channel>& channel);
 
     TestService::Stub* Get();
 
diff --git a/test/cpp/interop/server_helper.h b/test/cpp/interop/server_helper.h
index 237c33cd0cd..ee72697b5e9 100644
--- a/test/cpp/interop/server_helper.h
+++ b/test/cpp/interop/server_helper.h
@@ -37,7 +37,7 @@ std::shared_ptr<ServerCredentials> CreateInteropServerCredentials();
 
 class InteropServerContextInspector {
  public:
-  InteropServerContextInspector(const ::grpc::ServerContext& context);
+  explicit InteropServerContextInspector(const ::grpc::ServerContext& context);
 
   // Inspector methods, able to peek inside ServerContext, follow.
   std::shared_ptr<const AuthContext> GetAuthContext() const;
diff --git a/test/cpp/interop/stress_interop_client.h b/test/cpp/interop/stress_interop_client.h
index eb2ec415af6..653df916542 100644
--- a/test/cpp/interop/stress_interop_client.h
+++ b/test/cpp/interop/stress_interop_client.h
@@ -77,7 +77,8 @@ const vector<pair<TestCaseType, std::string>> kTestCaseList = {
 class WeightedRandomTestSelector {
  public:
   // Takes a vector of <test_case, weight> pairs as the input
-  WeightedRandomTestSelector(const vector<pair<TestCaseType, int>>& tests);
+  explicit WeightedRandomTestSelector(
+      const vector<pair<TestCaseType, int>>& tests);
 
   // Returns a weighted-randomly chosen test case based on the test cases and
   // weights passed in the constructor
diff --git a/test/cpp/interop/xds_interop_server.cc b/test/cpp/interop/xds_interop_server.cc
index fa8f3a780e0..99551737d9c 100644
--- a/test/cpp/interop/xds_interop_server.cc
+++ b/test/cpp/interop/xds_interop_server.cc
@@ -50,7 +50,7 @@ using grpc::testing::TestService;
 
 class TestServiceImpl : public TestService::Service {
  public:
-  TestServiceImpl(const std::string& i) : hostname_(i) {}
+  explicit TestServiceImpl(const std::string& i) : hostname_(i) {}
 
   Status UnaryCall(ServerContext* context, const SimpleRequest* request,
                    SimpleResponse* response) override {
diff --git a/test/cpp/microbenchmarks/bm_call_create.cc b/test/cpp/microbenchmarks/bm_call_create.cc
index 4b114167c43..e167f40bbe4 100644
--- a/test/cpp/microbenchmarks/bm_call_create.cc
+++ b/test/cpp/microbenchmarks/bm_call_create.cc
@@ -76,7 +76,7 @@ BENCHMARK(BM_Zalloc)
 
 class BaseChannelFixture {
  public:
-  BaseChannelFixture(grpc_channel* channel) : channel_(channel) {}
+  explicit BaseChannelFixture(grpc_channel* channel) : channel_(channel) {}
   ~BaseChannelFixture() { grpc_channel_destroy(channel_); }
 
   grpc_channel* channel() const { return channel_; }
diff --git a/test/cpp/microbenchmarks/bm_chttp2_transport.cc b/test/cpp/microbenchmarks/bm_chttp2_transport.cc
index 220504b3de8..3c8822a4d65 100644
--- a/test/cpp/microbenchmarks/bm_chttp2_transport.cc
+++ b/test/cpp/microbenchmarks/bm_chttp2_transport.cc
@@ -181,7 +181,7 @@ std::unique_ptr<TestClosure> MakeTestClosure(F f) {
 template <class F>
 grpc_closure* MakeOnceClosure(F f) {
   struct C : public grpc_closure {
-    C(const F& f) : f_(f) {}
+    explicit C(const F& f) : f_(f) {}
     F f_;
     static void Execute(void* arg, grpc_error* error) {
       static_cast<C*>(arg)->f_(error);
@@ -194,7 +194,7 @@ grpc_closure* MakeOnceClosure(F f) {
 
 class Stream {
  public:
-  Stream(Fixture* f) : f_(f) {
+  explicit Stream(Fixture* f) : f_(f) {
     stream_size_ = grpc_transport_stream_size(f->transport());
     stream_ = gpr_malloc(stream_size_);
     arena_ = grpc_core::Arena::Create(4096);
diff --git a/test/cpp/microbenchmarks/bm_threadpool.cc b/test/cpp/microbenchmarks/bm_threadpool.cc
index d403f8f0918..cb6110a8187 100644
--- a/test/cpp/microbenchmarks/bm_threadpool.cc
+++ b/test/cpp/microbenchmarks/bm_threadpool.cc
@@ -37,7 +37,7 @@ namespace testing {
 // the count reaches 0.
 class BlockingCounter {
  public:
-  BlockingCounter(int count) : count_(count) {}
+  explicit BlockingCounter(int count) : count_(count) {}
   void DecrementCount() {
     std::lock_guard<std::mutex> l(mu_);
     count_--;
@@ -130,7 +130,7 @@ BENCHMARK_TEMPLATE(ThreadPoolAddAnother, 2048)
 // A functor class that will delete self on end of running.
 class SuicideFunctorForAdd : public grpc_experimental_completion_queue_functor {
  public:
-  SuicideFunctorForAdd(BlockingCounter* counter) : counter_(counter) {
+  explicit SuicideFunctorForAdd(BlockingCounter* counter) : counter_(counter) {
     functor_run = &SuicideFunctorForAdd::Run;
     inlineable = false;
     internal_next = this;
diff --git a/test/cpp/microbenchmarks/fullstack_context_mutators.h b/test/cpp/microbenchmarks/fullstack_context_mutators.h
index 06a1d78f153..82e05e8dc28 100644
--- a/test/cpp/microbenchmarks/fullstack_context_mutators.h
+++ b/test/cpp/microbenchmarks/fullstack_context_mutators.h
@@ -52,7 +52,7 @@ auto MakeVector(size_t length, F f) -> std::vector<decltype(f())> {
 class NoOpMutator {
  public:
   template <class ContextType>
-  NoOpMutator(ContextType* /*context*/) {}
+  explicit NoOpMutator(ContextType* /*context*/) {}
 };
 
 template <int length>
@@ -100,7 +100,7 @@ class RandomAsciiMetadata {
 template <class Generator, int kNumKeys>
 class Client_AddMetadata : public NoOpMutator {
  public:
-  Client_AddMetadata(ClientContext* context) : NoOpMutator(context) {
+  explicit Client_AddMetadata(ClientContext* context) : NoOpMutator(context) {
     for (int i = 0; i < kNumKeys; i++) {
       context->AddMetadata(Generator::Key(), Generator::Value());
     }
@@ -110,7 +110,8 @@ class Client_AddMetadata : public NoOpMutator {
 template <class Generator, int kNumKeys>
 class Server_AddInitialMetadata : public NoOpMutator {
  public:
-  Server_AddInitialMetadata(ServerContext* context) : NoOpMutator(context) {
+  explicit Server_AddInitialMetadata(ServerContext* context)
+      : NoOpMutator(context) {
     for (int i = 0; i < kNumKeys; i++) {
       context->AddInitialMetadata(Generator::Key(), Generator::Value());
     }
diff --git a/test/cpp/microbenchmarks/fullstack_fixtures.h b/test/cpp/microbenchmarks/fullstack_fixtures.h
index 9ba190b691f..b5e8028173d 100644
--- a/test/cpp/microbenchmarks/fullstack_fixtures.h
+++ b/test/cpp/microbenchmarks/fullstack_fixtures.h
@@ -111,8 +111,9 @@ class FullstackFixture : public BaseFixture {
 
 class TCP : public FullstackFixture {
  public:
-  TCP(Service* service, const FixtureConfiguration& fixture_configuration =
-                            FixtureConfiguration())
+  explicit TCP(Service* service,
+               const FixtureConfiguration& fixture_configuration =
+                   FixtureConfiguration())
       : FullstackFixture(service, fixture_configuration, MakeAddress(&port_)) {}
 
   ~TCP() override { grpc_recycle_unused_port(port_); }
@@ -130,8 +131,9 @@ class TCP : public FullstackFixture {
 
 class UDS : public FullstackFixture {
  public:
-  UDS(Service* service, const FixtureConfiguration& fixture_configuration =
-                            FixtureConfiguration())
+  explicit UDS(Service* service,
+               const FixtureConfiguration& fixture_configuration =
+                   FixtureConfiguration())
       : FullstackFixture(service, fixture_configuration, MakeAddress(&port_)) {}
 
   ~UDS() override { grpc_recycle_unused_port(port_); }
@@ -150,9 +152,9 @@ class UDS : public FullstackFixture {
 
 class InProcess : public FullstackFixture {
  public:
-  InProcess(Service* service,
-            const FixtureConfiguration& fixture_configuration =
-                FixtureConfiguration())
+  explicit InProcess(Service* service,
+                     const FixtureConfiguration& fixture_configuration =
+                         FixtureConfiguration())
       : FullstackFixture(service, fixture_configuration, "") {}
   ~InProcess() override {}
 };
@@ -241,8 +243,9 @@ class EndpointPairFixture : public BaseFixture {
 
 class SockPair : public EndpointPairFixture {
  public:
-  SockPair(Service* service, const FixtureConfiguration& fixture_configuration =
-                                 FixtureConfiguration())
+  explicit SockPair(Service* service,
+                    const FixtureConfiguration& fixture_configuration =
+                        FixtureConfiguration())
       : EndpointPairFixture(service,
                             grpc_iomgr_create_endpoint_pair("test", nullptr),
                             fixture_configuration) {}
@@ -287,9 +290,9 @@ class InProcessCHTTP2WithExplicitStats : public EndpointPairFixture {
 
 class InProcessCHTTP2 : public InProcessCHTTP2WithExplicitStats {
  public:
-  InProcessCHTTP2(Service* service,
-                  const FixtureConfiguration& fixture_configuration =
-                      FixtureConfiguration())
+  explicit InProcessCHTTP2(Service* service,
+                           const FixtureConfiguration& fixture_configuration =
+                               FixtureConfiguration())
       : InProcessCHTTP2WithExplicitStats(service,
                                          grpc_passthru_endpoint_stats_create(),
                                          fixture_configuration) {}
@@ -313,7 +316,8 @@ class MinStackConfiguration : public FixtureConfiguration {
 template <class Base>
 class MinStackize : public Base {
  public:
-  MinStackize(Service* service) : Base(service, MinStackConfiguration()) {}
+  explicit MinStackize(Service* service)
+      : Base(service, MinStackConfiguration()) {}
 };
 
 typedef MinStackize<TCP> MinTCP;
diff --git a/test/cpp/qps/client_callback.cc b/test/cpp/qps/client_callback.cc
index bc8fdb52175..d0d3d4c30e1 100644
--- a/test/cpp/qps/client_callback.cc
+++ b/test/cpp/qps/client_callback.cc
@@ -45,7 +45,7 @@ namespace testing {
  * Maintains context info per RPC
  */
 struct CallbackClientRpcContext {
-  CallbackClientRpcContext(BenchmarkService::Stub* stub)
+  explicit CallbackClientRpcContext(BenchmarkService::Stub* stub)
       : alarm_(nullptr), stub_(stub) {}
 
   ~CallbackClientRpcContext() {}
@@ -64,7 +64,7 @@ static std::unique_ptr<BenchmarkService::Stub> BenchmarkStubCreator(
 class CallbackClient
     : public ClientImpl<BenchmarkService::Stub, SimpleRequest> {
  public:
-  CallbackClient(const ClientConfig& config)
+  explicit CallbackClient(const ClientConfig& config)
       : ClientImpl<BenchmarkService::Stub, SimpleRequest>(
             config, BenchmarkStubCreator) {
     num_threads_ = NumThreads(config);
@@ -144,7 +144,8 @@ class CallbackClient
 
 class CallbackUnaryClient final : public CallbackClient {
  public:
-  CallbackUnaryClient(const ClientConfig& config) : CallbackClient(config) {
+  explicit CallbackUnaryClient(const ClientConfig& config)
+      : CallbackClient(config) {
     for (int ch = 0; ch < config.client_channels(); ch++) {
       for (int i = 0; i < config.outstanding_rpcs_per_channel(); i++) {
         ctx_.emplace_back(
@@ -214,7 +215,7 @@ class CallbackUnaryClient final : public CallbackClient {
 
 class CallbackStreamingClient : public CallbackClient {
  public:
-  CallbackStreamingClient(const ClientConfig& config)
+  explicit CallbackStreamingClient(const ClientConfig& config)
       : CallbackClient(config),
         messages_per_stream_(config.messages_per_stream()) {
     for (int ch = 0; ch < config.client_channels(); ch++) {
@@ -244,7 +245,7 @@ class CallbackStreamingClient : public CallbackClient {
 
 class CallbackStreamingPingPongClient : public CallbackStreamingClient {
  public:
-  CallbackStreamingPingPongClient(const ClientConfig& config)
+  explicit CallbackStreamingPingPongClient(const ClientConfig& config)
       : CallbackStreamingClient(config) {}
   ~CallbackStreamingPingPongClient() override {}
 };
@@ -342,7 +343,7 @@ class CallbackStreamingPingPongReactor final
 class CallbackStreamingPingPongClientImpl final
     : public CallbackStreamingPingPongClient {
  public:
-  CallbackStreamingPingPongClientImpl(const ClientConfig& config)
+  explicit CallbackStreamingPingPongClientImpl(const ClientConfig& config)
       : CallbackStreamingPingPongClient(config) {
     for (size_t i = 0; i < total_outstanding_rpcs_; i++) {
       reactor_.emplace_back(
diff --git a/test/cpp/qps/client_sync.cc b/test/cpp/qps/client_sync.cc
index f042a035825..72fff1a8533 100644
--- a/test/cpp/qps/client_sync.cc
+++ b/test/cpp/qps/client_sync.cc
@@ -50,7 +50,7 @@ static std::unique_ptr<BenchmarkService::Stub> BenchmarkStubCreator(
 class SynchronousClient
     : public ClientImpl<BenchmarkService::Stub, SimpleRequest> {
  public:
-  SynchronousClient(const ClientConfig& config)
+  explicit SynchronousClient(const ClientConfig& config)
       : ClientImpl<BenchmarkService::Stub, SimpleRequest>(
             config, BenchmarkStubCreator) {
     num_threads_ =
@@ -111,7 +111,7 @@ class SynchronousClient
 
 class SynchronousUnaryClient final : public SynchronousClient {
  public:
-  SynchronousUnaryClient(const ClientConfig& config)
+  explicit SynchronousUnaryClient(const ClientConfig& config)
       : SynchronousClient(config) {
     StartThreads(num_threads_);
   }
@@ -143,7 +143,7 @@ class SynchronousUnaryClient final : public SynchronousClient {
 template <class StreamType>
 class SynchronousStreamingClient : public SynchronousClient {
  public:
-  SynchronousStreamingClient(const ClientConfig& config)
+  explicit SynchronousStreamingClient(const ClientConfig& config)
       : SynchronousClient(config),
         context_(num_threads_),
         stream_(num_threads_),
@@ -219,7 +219,7 @@ class SynchronousStreamingPingPongClient final
     : public SynchronousStreamingClient<
           grpc::ClientReaderWriter<SimpleRequest, SimpleResponse>> {
  public:
-  SynchronousStreamingPingPongClient(const ClientConfig& config)
+  explicit SynchronousStreamingPingPongClient(const ClientConfig& config)
       : SynchronousStreamingClient(config) {}
   ~SynchronousStreamingPingPongClient() override {
     CleanupAllStreams(
@@ -276,7 +276,7 @@ class SynchronousStreamingPingPongClient final
 class SynchronousStreamingFromClientClient final
     : public SynchronousStreamingClient<grpc::ClientWriter<SimpleRequest>> {
  public:
-  SynchronousStreamingFromClientClient(const ClientConfig& config)
+  explicit SynchronousStreamingFromClientClient(const ClientConfig& config)
       : SynchronousStreamingClient(config), last_issue_(num_threads_) {}
   ~SynchronousStreamingFromClientClient() override {
     CleanupAllStreams(
@@ -329,7 +329,7 @@ class SynchronousStreamingFromClientClient final
 class SynchronousStreamingFromServerClient final
     : public SynchronousStreamingClient<grpc::ClientReader<SimpleResponse>> {
  public:
-  SynchronousStreamingFromServerClient(const ClientConfig& config)
+  explicit SynchronousStreamingFromServerClient(const ClientConfig& config)
       : SynchronousStreamingClient(config), last_recv_(num_threads_) {}
   ~SynchronousStreamingFromServerClient() override {}
 
@@ -375,7 +375,7 @@ class SynchronousStreamingBothWaysClient final
     : public SynchronousStreamingClient<
           grpc::ClientReaderWriter<SimpleRequest, SimpleResponse>> {
  public:
-  SynchronousStreamingBothWaysClient(const ClientConfig& config)
+  explicit SynchronousStreamingBothWaysClient(const ClientConfig& config)
       : SynchronousStreamingClient(config) {}
   ~SynchronousStreamingBothWaysClient() override {
     CleanupAllStreams(
diff --git a/test/cpp/qps/qps_worker.cc b/test/cpp/qps/qps_worker.cc
index 54a1b20baee..99c0e34b3ad 100644
--- a/test/cpp/qps/qps_worker.cc
+++ b/test/cpp/qps/qps_worker.cc
@@ -157,7 +157,7 @@ class WorkerServiceImpl final : public WorkerService::Service {
   // Protect against multiple clients using this worker at once.
   class InstanceGuard {
    public:
-    InstanceGuard(WorkerServiceImpl* impl)
+    explicit InstanceGuard(WorkerServiceImpl* impl)
         : impl_(impl), acquired_(impl->TryAcquireInstance()) {}
     ~InstanceGuard() {
       if (acquired_) {
diff --git a/test/cpp/qps/report.h b/test/cpp/qps/report.h
index b00b0a311ff..d85dea4349b 100644
--- a/test/cpp/qps/report.h
+++ b/test/cpp/qps/report.h
@@ -37,7 +37,7 @@ namespace testing {
 class Reporter {
  public:
   /** Construct a reporter with the given \a name. */
-  Reporter(const string& name) : name_(name) {}
+  explicit Reporter(const string& name) : name_(name) {}
 
   virtual ~Reporter() {}
 
@@ -94,7 +94,7 @@ class CompositeReporter : public Reporter {
 /** Reporter to gpr_log(GPR_INFO). */
 class GprLogReporter : public Reporter {
  public:
-  GprLogReporter(const string& name) : Reporter(name) {}
+  explicit GprLogReporter(const string& name) : Reporter(name) {}
 
  private:
   void ReportQPS(const ScenarioResult& result) override;
diff --git a/test/cpp/server/server_builder_with_socket_mutator_test.cc b/test/cpp/server/server_builder_with_socket_mutator_test.cc
index ab4308007ce..b0bedeb3882 100644
--- a/test/cpp/server/server_builder_with_socket_mutator_test.cc
+++ b/test/cpp/server/server_builder_with_socket_mutator_test.cc
@@ -74,7 +74,8 @@ void mock_socket_mutator_destroy(grpc_socket_mutator* m) {
 
 class MockSocketMutatorServerBuilderOption : public grpc::ServerBuilderOption {
  public:
-  MockSocketMutatorServerBuilderOption(MockSocketMutator* mock_socket_mutator)
+  explicit MockSocketMutatorServerBuilderOption(
+      MockSocketMutator* mock_socket_mutator)
       : mock_socket_mutator_(mock_socket_mutator) {}
 
   void UpdateArguments(ChannelArguments* args) override {
diff --git a/test/cpp/util/grpc_tool_test.cc b/test/cpp/util/grpc_tool_test.cc
index bf4eeaf6608..7cd2751417c 100644
--- a/test/cpp/util/grpc_tool_test.cc
+++ b/test/cpp/util/grpc_tool_test.cc
@@ -133,7 +133,7 @@ const int kServerDefaultResponseStreamsToSend = 3;
 
 class TestCliCredentials final : public grpc::testing::CliCredentials {
  public:
-  TestCliCredentials(bool secure = false) : secure_(secure) {}
+  explicit TestCliCredentials(bool secure = false) : secure_(secure) {}
   std::shared_ptr<grpc::ChannelCredentials> GetChannelCredentials()
       const override {
     if (!secure_) {
diff --git a/test/cpp/util/subprocess.h b/test/cpp/util/subprocess.h
index 0fe56d40e98..d75de16b872 100644
--- a/test/cpp/util/subprocess.h
+++ b/test/cpp/util/subprocess.h
@@ -29,7 +29,7 @@ namespace grpc {
 
 class SubProcess {
  public:
-  SubProcess(const std::vector<std::string>& args);
+  explicit SubProcess(const std::vector<std::string>& args);
   ~SubProcess();
 
   int Join();