diff --git a/google/auth/_default.py b/google/auth/_default.py
index 3f6993a..74b96b3 100644
--- a/google/auth/_default.py
+++ b/google/auth/_default.py
@@ -23,6 +23,7 @@
 import os
 
 from google.auth import _cloud_sdk
+from google.auth import app_engine
 from google.auth import compute_engine
 from google.auth import environment_vars
 from google.auth import exceptions
@@ -150,7 +151,12 @@
 
 def _get_gae_credentials():
     """Gets Google App Engine App Identity credentials and project ID."""
-    return None, None
+    try:
+        credentials = app_engine.Credentials()
+        project_id = app_engine.get_project_id()
+        return credentials, project_id
+    except EnvironmentError:
+        return None, None
 
 
 def _get_gce_credentials(request=None):
diff --git a/google/auth/app_engine.py b/google/auth/app_engine.py
index 6f32b23..d20ddf6 100644
--- a/google/auth/app_engine.py
+++ b/google/auth/app_engine.py
@@ -33,6 +33,21 @@
     app_identity = None
 
 
+def get_project_id():
+    """Gets the project ID for the current App Engine application.
+
+    Returns:
+        str: The project ID
+
+    Raises:
+        EnvironmentError: If the App Engine APIs are unavailable.
+    """
+    if app_identity is None:
+        raise EnvironmentError(
+            'The App Engine APIs are not available.')
+    return app_identity.get_application_id()
+
+
 class Credentials(credentials.Scoped, credentials.Signing,
                   credentials.Credentials):
     """App Engine standard environment credentials.