diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index ac8d67ddd19..524a7b10504 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -964,7 +964,7 @@ class TestCase(object):
 
                 if item1 != item2:
                     differing += ('\nFirst differing element %d:\n%s\n%s\n' %
-                                 (i, item1, item2))
+                                 ((i,) + _common_shorten_repr(item1, item2)))
                     break
             else:
                 if (len1 == len2 and seq_type is None and
@@ -977,7 +977,7 @@ class TestCase(object):
                              'elements.\n' % (seq_type_name, len1 - len2))
                 try:
                     differing += ('First extra element %d:\n%s\n' %
-                                  (len2, seq1[len2]))
+                                  (len2, safe_repr(seq1[len2])))
                 except (TypeError, IndexError, NotImplementedError):
                     differing += ('Unable to index element %d '
                                   'of first %s\n' % (len2, seq_type_name))
@@ -986,7 +986,7 @@ class TestCase(object):
                              'elements.\n' % (seq_type_name, len2 - len1))
                 try:
                     differing += ('First extra element %d:\n%s\n' %
-                                  (len1, seq2[len1]))
+                                  (len1, safe_repr(seq2[len1])))
                 except (TypeError, IndexError, NotImplementedError):
                     differing += ('Unable to index element %d '
                                   'of second %s\n' % (len1, seq_type_name))
diff --git a/Lib/unittest/test/test_case.py b/Lib/unittest/test/test_case.py
index ada733b1ffb..1fb95dce2f9 100644
--- a/Lib/unittest/test/test_case.py
+++ b/Lib/unittest/test/test_case.py
@@ -1121,6 +1121,82 @@ test case
             error = str(e).split('\n', 1)[1]
             self.assertEqual(sample_text_error, error)
 
+    def testEqualityBytesWarning(self):
+        if sys.flags.bytes_warning:
+            def bytes_warning():
+                return self.assertWarnsRegex(BytesWarning,
+                            'Comparison between bytes and string')
+        else:
+            def bytes_warning():
+                return contextlib.ExitStack()
+
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertEqual('a', b'a')
+        with bytes_warning():
+            self.assertNotEqual('a', b'a')
+
+        a = [0, 'a']
+        b = [0, b'a']
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertListEqual(a, b)
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertTupleEqual(tuple(a), tuple(b))
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertSequenceEqual(a, tuple(b))
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertSequenceEqual(tuple(a), b)
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertSequenceEqual('a', b'a')
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertSetEqual(set(a), set(b))
+
+        with self.assertRaises(self.failureException):
+            self.assertListEqual(a, tuple(b))
+        with self.assertRaises(self.failureException):
+            self.assertTupleEqual(tuple(a), b)
+
+        a = [0, b'a']
+        b = [0]
+        with self.assertRaises(self.failureException):
+            self.assertListEqual(a, b)
+        with self.assertRaises(self.failureException):
+            self.assertTupleEqual(tuple(a), tuple(b))
+        with self.assertRaises(self.failureException):
+            self.assertSequenceEqual(a, tuple(b))
+        with self.assertRaises(self.failureException):
+            self.assertSequenceEqual(tuple(a), b)
+        with self.assertRaises(self.failureException):
+            self.assertSetEqual(set(a), set(b))
+
+        a = [0]
+        b = [0, b'a']
+        with self.assertRaises(self.failureException):
+            self.assertListEqual(a, b)
+        with self.assertRaises(self.failureException):
+            self.assertTupleEqual(tuple(a), tuple(b))
+        with self.assertRaises(self.failureException):
+            self.assertSequenceEqual(a, tuple(b))
+        with self.assertRaises(self.failureException):
+            self.assertSequenceEqual(tuple(a), b)
+        with self.assertRaises(self.failureException):
+            self.assertSetEqual(set(a), set(b))
+
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertDictEqual({'a': 0}, {b'a': 0})
+        with self.assertRaises(self.failureException):
+            self.assertDictEqual({}, {b'a': 0})
+        with self.assertRaises(self.failureException):
+            self.assertDictEqual({b'a': 0}, {})
+
+        with self.assertRaises(self.failureException):
+            self.assertCountEqual([b'a', b'a'], [b'a', b'a', b'a'])
+        with bytes_warning():
+            self.assertCountEqual(['a', b'a'], ['a', b'a'])
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertCountEqual(['a', 'a'], [b'a', b'a'])
+        with bytes_warning(), self.assertRaises(self.failureException):
+            self.assertCountEqual(['a', 'a', []], [b'a', b'a', []])
+
     def testAssertIsNone(self):
         self.assertIsNone(None)
         self.assertRaises(self.failureException, self.assertIsNone, False)
diff --git a/Misc/NEWS b/Misc/NEWS
index f24eeeac117..384f5252d13 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -256,6 +256,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #26837: assertSequenceEqual() now correctly outputs non-stringified
+  differing items (like bytes in the -b mode).  This affects assertListEqual()
+  and assertTupleEqual().
+
 - Issue #26041: Remove "will be removed in Python 3.7" from deprecation
   messages of platform.dist() and platform.linux_distribution().
   Patch by Kumaripaba Miyurusara Athukorala.