diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6ce00ecacdf..03e1f5779ca 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -111,6 +111,14 @@ endif()
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${_gRPC_C_CXX_FLAGS}")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${_gRPC_C_CXX_FLAGS}")
 
+if(CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
+  # Windows release builds don't set NDEBUG in NASM flags automatically.
+  # boringssl's cmake already sets this flag for "Release" build,
+  # but gRPC C# artifacts are being built under the RelWithDebInfo configuration
+  # https://github.com/google/boringssl/blob/f7b830d8df9f5578c748aa0283d44c59ea7eeb25/CMakeLists.txt#L64
+  set(CMAKE_ASM_NASM_FLAGS "${CMAKE_ASM_NASM_FLAGS} -DNDEBUG")
+endif()
+
 if (gRPC_USE_PROTO_LITE)
   set(_gRPC_PROTOBUF_LIBRARY_NAME "libprotobuf-lite")
   add_definitions("-DGRPC_USE_PROTO_LITE")
diff --git a/templates/CMakeLists.txt.template b/templates/CMakeLists.txt.template
index 77769cb93bf..860f6e74f69 100644
--- a/templates/CMakeLists.txt.template
+++ b/templates/CMakeLists.txt.template
@@ -160,6 +160,14 @@
   set(CMAKE_C_FLAGS "<%text>${CMAKE_C_FLAGS} ${_gRPC_C_CXX_FLAGS}</%text>")
   set(CMAKE_CXX_FLAGS "<%text>${CMAKE_CXX_FLAGS} ${_gRPC_C_CXX_FLAGS}</%text>")
 
+  if(CMAKE_BUILD_TYPE STREQUAL "RelWithDebInfo")
+    # Windows release builds don't set NDEBUG in NASM flags automatically.
+    # boringssl's cmake already sets this flag for "Release" build,
+    # but gRPC C# artifacts are being built under the RelWithDebInfo configuration
+    # https://github.com/google/boringssl/blob/f7b830d8df9f5578c748aa0283d44c59ea7eeb25/CMakeLists.txt#L64
+    set(CMAKE_ASM_NASM_FLAGS "<%text>${CMAKE_ASM_NASM_FLAGS}</%text> -DNDEBUG")
+  endif()
+
   if (gRPC_USE_PROTO_LITE)
     set(_gRPC_PROTOBUF_LIBRARY_NAME "libprotobuf-lite")
     add_definitions("-DGRPC_USE_PROTO_LITE")