diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pxd.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pxd.pxi
index f1a7a996644..e69200c7376 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pxd.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pxd.pxi
@@ -24,6 +24,13 @@ cdef extern from "<queue>" namespace "std" nogil:
         size_t size()
 
 
+cdef extern from "<mutex>" namespace "std" nogil:
+    cdef cppclass mutex:
+        mutex()
+        void lock()
+        void unlock()
+
+
 ctypedef queue[grpc_event] cpp_event_queue
 
 
@@ -45,6 +52,7 @@ cdef class BaseCompletionQueue:
 cdef class PollerCompletionQueue(BaseCompletionQueue):
     cdef bint _shutdown
     cdef cpp_event_queue _queue
+    cdef mutex _queue_mutex
     cdef object _poller_thread
     cdef int _write_fd
     cdef object _read_socket
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pyx.pxi
index 8c4fa014130..15d2e18f3d7 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/aio/completion_queue.pyx.pxi
@@ -67,7 +67,9 @@ cdef class PollerCompletionQueue(BaseCompletionQueue):
             elif event.type == GRPC_QUEUE_SHUTDOWN:
                 self._shutdown = True
             else:
+                self._queue_mutex.lock()
                 self._queue.push(event)
+                self._queue_mutex.unlock()
                 _unified_socket_write(self._write_fd)
 
     def _poll_wrapper(self):
@@ -85,9 +87,15 @@ cdef class PollerCompletionQueue(BaseCompletionQueue):
         cdef grpc_event event
         cdef CallbackContext *context
 
-        while not self._queue.empty():
-            event = self._queue.front()
-            self._queue.pop()
+        while True:
+            self._queue_mutex.lock()
+            if self._queue.empty():
+                self._queue_mutex.unlock()
+                break
+            else:
+                event = self._queue.front()
+                self._queue.pop()
+                self._queue_mutex.unlock()
 
             context = <CallbackContext *>event.tag
             loop = <object>context.loop