diff --git a/core/google/cloud/_testing.py b/core/google/cloud/_testing.py
index 49eb35ad50ae..880536f8aa45 100644
--- a/core/google/cloud/_testing.py
+++ b/core/google/cloud/_testing.py
@@ -77,6 +77,10 @@ def _make_grpc_failed_precondition(self):
         from grpc import StatusCode
         return self._make_grpc_error(StatusCode.FAILED_PRECONDITION)
 
+    def _make_grpc_deadline_exceeded(self):
+        from grpc import StatusCode
+        return self._make_grpc_error(StatusCode.DEADLINE_EXCEEDED)
+
 
 class _GAXPageIterator(object):
 
diff --git a/pubsub/google/cloud/pubsub/_gax.py b/pubsub/google/cloud/pubsub/_gax.py
index 57bf688486aa..11ab7d4aac7b 100644
--- a/pubsub/google/cloud/pubsub/_gax.py
+++ b/pubsub/google/cloud/pubsub/_gax.py
@@ -413,8 +413,15 @@ def subscription_pull(self, subscription_path, return_immediately=False,
                 subscription_path, max_messages,
                 return_immediately=return_immediately)
         except GaxError as exc:
-            if exc_to_code(exc.cause) == StatusCode.NOT_FOUND:
+            code = exc_to_code(exc.cause)
+            if code == StatusCode.NOT_FOUND:
                 raise NotFound(subscription_path)
+            elif code == StatusCode.DEADLINE_EXCEEDED:
+                # NOTE: The JSON-over-HTTP API returns a 200 with an empty
+                #       response when ``return_immediately`` is ``False``, so
+                #       we "mutate" the gRPC error into a non-error to conform.
+                if not return_immediately:
+                    return []
             raise
         return [_received_message_pb_to_mapping(rmpb)
                 for rmpb in response_pb.received_messages]
diff --git a/pubsub/unit_tests/test__gax.py b/pubsub/unit_tests/test__gax.py
index 43d9804b90a9..decf9a25c068 100644
--- a/pubsub/unit_tests/test__gax.py
+++ b/pubsub/unit_tests/test__gax.py
@@ -764,6 +764,24 @@ def test_subscription_pull_defaults_error(self):
         self.assertFalse(return_immediately)
         self.assertIsNone(options)
 
+    def test_subscription_pull_deadline_exceeded(self):
+        client = _Client(self.PROJECT)
+        gax_api = _GAXSubscriberAPI(_deadline_exceeded_gax_error=True)
+        api = self._make_one(gax_api, client)
+
+        result = api.subscription_pull(self.SUB_PATH)
+        self.assertEqual(result, [])
+
+    def test_subscription_pull_deadline_exceeded_return_immediately(self):
+        from google.gax.errors import GaxError
+
+        client = _Client(self.PROJECT)
+        gax_api = _GAXSubscriberAPI(_deadline_exceeded_gax_error=True)
+        api = self._make_one(gax_api, client)
+
+        with self.assertRaises(GaxError):
+            api.subscription_pull(self.SUB_PATH, return_immediately=True)
+
     def test_subscription_acknowledge_hit(self):
         ACK_ID1 = 'DEADBEEF'
         ACK_ID2 = 'BEADCAFE'
@@ -1075,6 +1093,7 @@ class _GAXSubscriberAPI(_GAXBaseAPI):
     _modify_push_config_ok = False
     _acknowledge_ok = False
     _modify_ack_deadline_ok = False
+    _deadline_exceeded_gax_error = False
 
     def list_subscriptions(self, project, page_size, options=None):
         self._list_subscriptions_called_with = (project, page_size, options)
@@ -1124,6 +1143,9 @@ def pull(self, name, max_messages, return_immediately, options=None):
             name, max_messages, return_immediately, options)
         if self._random_gax_error:
             raise GaxError('error')
+        if self._deadline_exceeded_gax_error:
+            raise GaxError('deadline exceeded',
+                           self._make_grpc_deadline_exceeded())
         try:
             return self._pull_response
         except AttributeError: