diff --git a/core/google/cloud/client.py b/core/google/cloud/client.py
index 6a7fb1fe5554..b03b54197441 100644
--- a/core/google/cloud/client.py
+++ b/core/google/cloud/client.py
@@ -33,6 +33,9 @@
     "for help on authentication with this library."
 )
 
+# Default timeout for auth requests.
+_CREDENTIALS_REFRESH_TIMEOUT = 300
+
 
 class _ClientFactoryMixin(object):
     """Mixin to allow factories that create credentials.
@@ -153,7 +156,8 @@ def _http(self):
         """
         if self._http_internal is None:
             self._http_internal = google.auth.transport.requests.AuthorizedSession(
-                self._credentials
+                self._credentials,
+                refresh_timeout=_CREDENTIALS_REFRESH_TIMEOUT,
             )
         return self._http_internal
 
diff --git a/core/tests/unit/test_client.py b/core/tests/unit/test_client.py
index 43830f902fbd..7aec69ffc701 100644
--- a/core/tests/unit/test_client.py
+++ b/core/tests/unit/test_client.py
@@ -122,6 +122,7 @@ def test__http_property_existing(self):
         self.assertIs(client._http, http)
 
     def test__http_property_new(self):
+        from google.cloud.client import _CREDENTIALS_REFRESH_TIMEOUT
         credentials = _make_credentials()
         client = self._make_one(credentials=credentials)
         self.assertIsNone(client._http_internal)
@@ -133,7 +134,7 @@ def test__http_property_new(self):
         with authorized_session_patch as AuthorizedSession:
             self.assertIs(client._http, mock.sentinel.http)
             # Check the mock.
-            AuthorizedSession.assert_called_once_with(credentials)
+            AuthorizedSession.assert_called_once_with(credentials, refresh_timeout=_CREDENTIALS_REFRESH_TIMEOUT)
             # Make sure the cached value is used on subsequent access.
             self.assertIs(client._http_internal, mock.sentinel.http)
             self.assertIs(client._http, mock.sentinel.http)