diff --git a/lower-constraints.txt b/lower-constraints.txt
index 3e41876e0..3618460bd 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -43,7 +43,6 @@ linecache2==1.0.0
 Mako==0.4.0
 MarkupSafe==1.0
 mccabe==0.2.1
-mock==2.0.0
 monasca-common==2.16.0
 monotonic==0.6
 mox3==0.20.0
diff --git a/monasca_api/tests/test_alarms.py b/monasca_api/tests/test_alarms.py
index 9180517dc..1cb5c097c 100644
--- a/monasca_api/tests/test_alarms.py
+++ b/monasca_api/tests/test_alarms.py
@@ -24,7 +24,7 @@ import falcon.testing
 import fixtures
 import testtools.matchers as matchers
 
-from mock import Mock
+from unittest.mock import Mock
 
 import oslo_config.fixture
 import six
diff --git a/monasca_api/tests/test_query_helpers.py b/monasca_api/tests/test_query_helpers.py
index 5dca8db11..a77929529 100644
--- a/monasca_api/tests/test_query_helpers.py
+++ b/monasca_api/tests/test_query_helpers.py
@@ -14,7 +14,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-from mock import Mock
+from unittest.mock import Mock
 
 from monasca_api.tests import base
 from monasca_api.v2.reference import helpers
diff --git a/monasca_api/tests/test_repositories.py b/monasca_api/tests/test_repositories.py
index 4a1a6f5b2..21075b1ff 100644
--- a/monasca_api/tests/test_repositories.py
+++ b/monasca_api/tests/test_repositories.py
@@ -21,7 +21,7 @@ from datetime import datetime
 
 import cassandra
 from cassandra.auth import PlainTextAuthProvider
-from mock import patch
+from unittest.mock import patch
 
 from oslo_config import cfg
 from oslo_utils import timeutils