diff -r 01676a4c16ff Lib/pathlib.py
--- a/Lib/pathlib.py	Sun Dec 08 10:06:04 2013 +0100
+++ b/Lib/pathlib.py	Sun Dec 08 12:24:02 2013 +0200
@@ -1096,7 +1096,7 @@
             except OSError as e:
                 if e.errno != ENOENT:
                     raise
-                self.parent.mkdir(mode, True)
+                self.parent.mkdir(parents=True)
                 self._accessor.mkdir(self, mode)
 
     def chmod(self, mode):
diff -r 01676a4c16ff Lib/test/test_pathlib.py
--- a/Lib/test/test_pathlib.py	Sun Dec 08 10:06:04 2013 +0100
+++ b/Lib/test/test_pathlib.py	Sun Dec 08 12:24:02 2013 +0200
@@ -1493,7 +1493,15 @@
         with self.assertRaises(OSError) as cm:
             p.mkdir(parents=True)
         self.assertEqual(cm.exception.errno, errno.EEXIST)
-        # XXX test `mode` arg
+        # test `mode` arg
+        mode = stat.S_IMODE(p.stat().st_mode) # default mode
+        p = self.cls(BASE, 'newdirD', 'newdirE')
+        p.mkdir(0o555, parents=True)
+        self.assertTrue(p.exists())
+        self.assertTrue(p.is_dir())
+        if os.name != 'nt':
+            self.assertEqual(stat.S_IMODE(p.stat().st_mode), 0o555 & mode)
+        self.assertEqual(stat.S_IMODE(p.parent.stat().st_mode), mode)
 
     @with_symlinks
     def test_symlink_to(self):