diff -r 7230978647a8 Lib/tempfile.py
--- a/Lib/tempfile.py	Fri Sep 26 12:33:06 2014 -0400
+++ b/Lib/tempfile.py	Fri Sep 26 17:01:28 2014 -0400
@@ -212,6 +212,16 @@
     raise FileExistsError(_errno.EEXIST,
                           "No usable temporary file name found")
 
+def _sanitize_dir(dir):
+    """A helper function to sanitize 'dir' argument."""
+
+    if dir is None:
+        return gettempdir()
+    else:
+        # Call abspath to resolve relative paths to absolute ones,
+        # see issue #20267.
+        return _os.path.abspath(dir)
+
 
 # User visible interfaces.
 
@@ -259,8 +269,7 @@
     Caller is responsible for deleting the file when done with it.
     """
 
-    if dir is None:
-        dir = gettempdir()
+    dir = _sanitize_dir(dir)
 
     if text:
         flags = _text_openflags
@@ -283,8 +292,7 @@
     Caller is responsible for deleting the directory when done with it.
     """
 
-    if dir is None:
-        dir = gettempdir()
+    dir = _sanitize_dir(dir)
 
     names = _get_candidate_names()
 
@@ -317,8 +325,7 @@
 ##    _warn("mktemp is a potential security risk to your program",
 ##          RuntimeWarning, stacklevel=2)
 
-    if dir is None:
-        dir = gettempdir()
+    dir = _sanitize_dir(dir)
 
     names = _get_candidate_names()
     for seq in range(TMP_MAX):
@@ -447,8 +454,7 @@
     when it is closed unless the 'delete' argument is set to False.
     """
 
-    if dir is None:
-        dir = gettempdir()
+    dir = _sanitize_dir(dir)
 
     flags = _bin_openflags
 
@@ -495,8 +501,7 @@
         """
         global _O_TMPFILE_WORKS
 
-        if dir is None:
-            dir = gettempdir()
+        dir = _sanitize_dir(dir)
 
         flags = _bin_openflags
         if _O_TMPFILE_WORKS:
diff -r 7230978647a8 Lib/test/test_tempfile.py
--- a/Lib/test/test_tempfile.py	Fri Sep 26 12:33:06 2014 -0400
+++ b/Lib/test/test_tempfile.py	Fri Sep 26 17:01:28 2014 -0400
@@ -1264,6 +1264,18 @@
             self.assertEqual(name, d.name)
         self.assertFalse(os.path.exists(name))
 
+    def test_different_cwd_upon_creation(self): # See issue #20267
+        # Relative paths are supported
+        old_cwd = os.getcwd()
+        try:
+            new_cwd = os.path.dirname(tempfile.mkdtemp())
+            os.chdir(new_cwd)
+            d = self.do_create(dir='.')
+        finally:
+            os.chdir(old_cwd)
+
+        self.assertTrue(new_cwd in d.name)
+        d.cleanup()
 
 def test_main():
     support.run_unittest(__name__)