diff --git a/fire/core_test.py b/fire/core_test.py
index 27c9f418..71e67e9a 100644
--- a/fire/core_test.py
+++ b/fire/core_test.py
@@ -22,7 +22,11 @@
 from fire import test_components as tc
 from fire import testutils
 from fire import trace
-import mock
+
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 
 import six
 
diff --git a/fire/fire_import_test.py b/fire/fire_import_test.py
index c5975681..3f379eff 100644
--- a/fire/fire_import_test.py
+++ b/fire/fire_import_test.py
@@ -18,7 +18,10 @@
 
 import fire
 from fire import testutils
-import mock
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 
 
 class FireImportTest(testutils.BaseTestCase):
diff --git a/fire/fire_test.py b/fire/fire_test.py
index 4f2ffb9b..69b58c76 100644
--- a/fire/fire_test.py
+++ b/fire/fire_test.py
@@ -25,7 +25,10 @@
 from fire import test_components as tc
 from fire import testutils
 
-import mock
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 import six
 
 
diff --git a/fire/interact_test.py b/fire/interact_test.py
index 29fa7597..7dea1f0e 100644
--- a/fire/interact_test.py
+++ b/fire/interact_test.py
@@ -21,7 +21,10 @@
 from fire import interact
 from fire import testutils
 
-import mock
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 
 
 try:
diff --git a/fire/testutils.py b/fire/testutils.py
index 3463fd50..628617d6 100644
--- a/fire/testutils.py
+++ b/fire/testutils.py
@@ -26,7 +26,10 @@
 from fire import core
 from fire import trace
 
-import mock
+try:
+  import mock  # python 2.x
+except ModuleNotFoundError:
+  from unittest import mock  # python 3.x
 import six