diff --git a/oauth2client/multistore_file.py b/oauth2client/multistore_file.py
index e1b39f7..4d2c091 100644
--- a/oauth2client/multistore_file.py
+++ b/oauth2client/multistore_file.py
@@ -125,6 +125,43 @@ def get_credential_storage_custom_key(
     An object derived from client.Storage for getting/setting the
     credential.
   """
+  multistore = _get_multistore(filename, warn_on_readonly=warn_on_readonly)
+  key = util.dict_to_tuple_key(key_dict)
+  return multistore._get_storage(key)
+
+
+@util.positional(1)
+def get_all_credential_keys(filename, warn_on_readonly=True):
+  """Gets all the registered credential keys in the given Multistore.
+
+  Args:
+    filename: The JSON file storing a set of credentials
+    warn_on_readonly: if True, log a warning if the store is readonly
+
+  Returns:
+    A list of the credential keys present in the file.  They are returned as
+    dictionaries that can be passed into get_credential_storage_custom_key to
+    get the actual credentials.
+  """
+  multistore = _get_multistore(filename, warn_on_readonly=warn_on_readonly)
+  multistore._lock()
+  try:
+    return multistore._get_all_credential_keys()
+  finally:
+    multistore._unlock()
+
+
+@util.positional(1)
+def _get_multistore(filename, warn_on_readonly=True):
+  """A helper method to initialize the multistore with proper locking.
+
+  Args:
+    filename: The JSON file storing a set of credentials
+    warn_on_readonly: if True, log a warning if the store is readonly
+
+  Returns:
+    A multistore object
+  """
   filename = os.path.expanduser(filename)
   _multistores_lock.acquire()
   try:
@@ -132,8 +169,7 @@ def get_credential_storage_custom_key(
         filename, _MultiStore(filename, warn_on_readonly=warn_on_readonly))
   finally:
     _multistores_lock.release()
-  key = util.dict_to_tuple_key(key_dict)
-  return multistore._get_storage(key)
+  return multistore
 
 
 class _MultiStore(object):
@@ -356,6 +392,14 @@ class _MultiStore(object):
       raw_creds.append({'key': raw_key, 'credential': raw_cred})
     self._locked_json_write(raw_data)
 
+  def _get_all_credential_keys(self):
+    """Gets all the registered credential keys in the multistore.
+
+    Returns:
+      A list of dictionaries corresponding to all the keys currently registered
+    """
+    return [dict(key) for key in self._data.keys()]
+
   def _get_credential(self, key):
     """Get a credential from the multistore.
 
diff --git a/tests/test_oauth2client_file.py b/tests/test_oauth2client_file.py
index c954d5e..786d708 100644
--- a/tests/test_oauth2client_file.py
+++ b/tests/test_oauth2client_file.py
@@ -60,14 +60,13 @@ class OAuth2ClientFileTests(unittest.TestCase):
     except OSError:
       pass
 
-  def create_test_credentials(self):
+  def create_test_credentials(self, client_id='some_client_id'):
     access_token = 'foo'
     client_secret = 'cOuDdkfjxxnv+'
     refresh_token = '1/0/a.df219fjls0'
     token_expiry = datetime.datetime.utcnow()
     token_uri = 'https://www.google.com/accounts/o8/oauth2/token'
     user_agent = 'refresh_checker/1.0'
-    client_id = 'some_client_id'
 
     credentials = OAuth2Credentials(
         access_token, client_id, client_secret,
@@ -285,5 +284,40 @@ class OAuth2ClientFileTests(unittest.TestCase):
 
     self.assertEqual(credentials.access_token, stored_credentials.access_token)
 
+
+  def test_multistore_file_get_all_keys(self):
+    # start with no keys
+    keys = multistore_file.get_all_credential_keys(FILENAME)
+    self.assertEquals([], keys)
+
+    # store credentials
+    credentials = self.create_test_credentials(client_id='client1')
+    custom_key = {'myapp': 'testing', 'clientid': 'client1'}
+    store1 = multistore_file.get_credential_storage_custom_key(
+        FILENAME, custom_key)
+    store1.put(credentials)
+
+    keys = multistore_file.get_all_credential_keys(FILENAME)
+    self.assertEquals([custom_key], keys)
+
+    # store more credentials
+    credentials = self.create_test_credentials(client_id='client2')
+    string_key = 'string_key'
+    store2 = multistore_file.get_credential_storage_custom_string_key(
+        FILENAME, string_key)
+    store2.put(credentials)
+
+    keys = multistore_file.get_all_credential_keys(FILENAME)
+    self.assertEquals(2, len(keys))
+    self.assertTrue(custom_key in keys)
+    self.assertTrue({'key': string_key} in keys)
+
+    # back to no keys
+    store1.delete()
+    store2.delete()
+    keys = multistore_file.get_all_credential_keys(FILENAME)
+    self.assertEquals([], keys)
+
+
 if __name__ == '__main__':
   unittest.main()