diff -r a30cdf366c02 Lib/unittest/mock.py
--- a/Lib/unittest/mock.py	Tue Jan 10 11:30:44 2017 +0800
+++ b/Lib/unittest/mock.py	Tue Jan 10 22:09:52 2017 +0200
@@ -238,6 +238,9 @@ class _SentinelObject(object):
     def __repr__(self):
         return 'sentinel.%s' % self.name
 
+    def __reduce__(self):
+        return 'sentinel.%s' % self.name
+
 
 class _Sentinel(object):
     """Access attributes to return a named object, usable as a sentinel."""
@@ -250,6 +253,9 @@ class _Sentinel(object):
             raise AttributeError
         return self._sentinels.setdefault(name, _SentinelObject(name))
 
+    def __reduce__(self):
+        return 'sentinel'
+
 
 sentinel = _Sentinel()
 
diff -r a30cdf366c02 Lib/unittest/test/testmock/testsentinel.py
--- a/Lib/unittest/test/testmock/testsentinel.py	Tue Jan 10 11:30:44 2017 +0800
+++ b/Lib/unittest/test/testmock/testsentinel.py	Tue Jan 10 22:09:52 2017 +0200
@@ -1,4 +1,6 @@
 import unittest
+import copy
+import pickle
 from unittest.mock import sentinel, DEFAULT
 
 
@@ -23,6 +25,17 @@ class SentinelTest(unittest.TestCase):
         # If this doesn't raise an AttributeError then help(mock) is broken
         self.assertRaises(AttributeError, lambda: sentinel.__bases__)
 
+    def testPickle(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL+1):
+            with self.subTest(protocol=proto):
+                pickled = pickle.dumps(sentinel.whatever, proto)
+                unpickled = pickle.loads(pickled)
+                self.assertIs(unpickled, sentinel.whatever)
+
+    def testCopy(self):
+        self.assertIs(copy.copy(sentinel.whatever), sentinel.whatever)
+        self.assertIs(copy.deepcopy(sentinel.whatever), sentinel.whatever)
+
 
 if __name__ == '__main__':
     unittest.main()