diff -r 3156dd82df2d Lib/_collections_abc.py
--- a/Lib/_collections_abc.py	Wed Jun 10 15:44:18 2015 -0700
+++ b/Lib/_collections_abc.py	Thu Jun 11 11:30:10 2015 -0700
@@ -672,13 +672,11 @@
         return set(it)
 
     def __contains__(self, item):
-        key, value = item
-        try:
-            v = self._mapping[key]
-        except KeyError:
+        # ItemsViews technically behave like sets of *tuple pairs*, and
+        # should reject lists, and improperly sized tuples.
+        if not isinstance(item, tuple) or len(item) != 2:
             return False
-        else:
-            return v == value
+        return item[0] in self._mapping and self._mapping[item[0]] == item[1]
 
     def __iter__(self):
         for key in self._mapping:
diff -r 3156dd82df2d Lib/test/test_collections.py
--- a/Lib/test/test_collections.py	Wed Jun 10 15:44:18 2015 -0700
+++ b/Lib/test/test_collections.py	Thu Jun 11 11:30:10 2015 -0700
@@ -1343,6 +1343,34 @@
         mss.clear()
         self.assertEqual(len(mss), 0)
 
+    def test_ItemsView_contains(self):
+        # Ensure that ItemsView mimics the behavior of dict.items()
+        class DictLikeMapping(Mapping):
+            def __init__(self, *args, **kwargs):
+                self._mapping = dict(*args, **kwargs)
+            def __getitem__(self, key):
+                return self._mapping[key]
+            def __iter__(self):
+                return iter(self._mapping)
+            def __len__(self):
+                return len(self._mapping)
+        d = DictLikeMapping(a=1, b=2, c=3)
+        ditems = d.items()
+        ddict = dict(d)
+        self.assertIsInstance(ditems, ItemsView)
+        # Corner cases designed to match dict.items(). In particular test the
+        # list and generator are not in the ItemsView as they are not tuples,
+        # which are the elements of a dict_view set.
+        NotIn = ["a", ("a", ), 1, ["a", 1], (i for i in ("a", 1))]
+        for el in NotIn:
+            self.assertNotIn(el, ditems)
+            self.assertEqual(el in ditems, el in ddict.items())
+        for el in zip(d.keys(), d.values()):
+            self.assertIn(el, ditems)
+        gen = NotIn[-1]
+        # Testing if x is in X should not affect x for items.
+        self.assertEqual("a", next(gen))
+
 ################################################################################
 ### Counter
 ################################################################################