diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -192,6 +192,23 @@
         d.extend(d)
         self.assertEqual(list(d), list('abcdabcd'))
 
+    def test_add(self):
+        d = deque()
+        e = deque('abc')
+        f = deque('def')
+        self.assertEqual(d + d, deque())
+        self.assertEqual(e + f, deque('abcdef'))
+        self.assertEqual(e + e, deque('abcabc'))
+        self.assertEqual(e + d, deque('abc'))
+        self.assertEqual(d + e, deque('abc'))
+        self.assertIsNot(d + d, deque())
+        self.assertIsNot(e + d, deque('abc'))
+        self.assertIsNot(d + e, deque('abc'))
+
+        g = deque('abcdef', maxlen=4)
+        h = deque('gh')
+        self.assertEqual(g + h, deque('efgh'))
+
     def test_iadd(self):
         d = deque('a')
         d += 'bcd'
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -498,6 +498,19 @@
     return (PyObject *)deque;
 }
 
+static PyObject *deque_copy(PyObject *deque);
+
+static PyObject *
+deque_concat(dequeobject *deque, PyObject *other)
+{
+    PyObject *new_deque;
+
+    new_deque = deque_copy((PyObject *)deque);
+    if (new_deque == NULL)
+        return NULL;
+    return deque_inplace_concat((dequeobject *)new_deque, other);
+}
+
 /* The rotate() method is part of the public API and is used internally
 as a primitive for other methods.
 
@@ -1291,7 +1304,7 @@
 
 static PySequenceMethods deque_as_sequence = {
     (lenfunc)deque_len,                 /* sq_length */
-    0,                                  /* sq_concat */
+    (binaryfunc)deque_concat,           /* sq_concat */
     0,                                  /* sq_repeat */
     (ssizeargfunc)deque_item,           /* sq_item */
     0,                                  /* sq_slice */