diff --git a/chalice/app.py b/chalice/app.py
index 77962f439..18fcb7e03 100644
--- a/chalice/app.py
+++ b/chalice/app.py
@@ -1436,7 +1436,8 @@ class AuthResponse(object):
                                    'PATCH', 'POST', 'PUT', 'GET']
 
     def __init__(self, routes: List[Union[str, 'AuthRoute']],
-                 principal_id: str, context: Optional[Dict[str, str]] = None):
+                 principal_id: str, context: Optional[Dict[str, str]] = None,
+                 usage_identifier_key: Optional[str] = None):
         self.routes: List[Union[str, 'AuthRoute']] = routes
         self.principal_id: str = principal_id
         # The request is used to generate full qualified ARNs
@@ -1445,13 +1446,17 @@ def __init__(self, routes: List[Union[str, 'AuthRoute']],
         if context is None:
             context = {}
         self.context: Dict[str, str] = context
+        self.usage_identifier_key: Optional[str] = usage_identifier_key
 
     def to_dict(self, request: AuthRequest) -> Dict[str, Any]:
-        return {
+        response = {
             'context': self.context,
             'principalId': self.principal_id,
             'policyDocument': self._generate_policy(request),
         }
+        if self.usage_identifier_key:
+            response['usageIdentifierKey'] = self.usage_identifier_key
+        return response
 
     def _generate_policy(self, request: AuthRequest) -> Dict[str, Any]:
         allowed_resources = self._generate_allowed_resources(request)
diff --git a/docs/source/api.rst b/docs/source/api.rst
index b9ca7613b..e271cce09 100644
--- a/docs/source/api.rst
+++ b/docs/source/api.rst
@@ -812,6 +812,11 @@ These classes are used when defining built-in authorizers in Chalice.
       will be accessible in the ``app.current_request.context``
       in all subsequent authorized requests for this user.
 
+   .. attribute:: usage_identifier_key
+
+      An optional string value that represents a usage plan's api
+      key if the ``apiKeySource`` for that plan is set to ``AUTHORIZER``.
+
 .. class:: AuthRoute(path, methods)
 
    This class be used in the ``routes`` attribute of a
diff --git a/tests/unit/test_app.py b/tests/unit/test_app.py
index ea33f3ce3..d681b9a76 100644
--- a/tests/unit/test_app.py
+++ b/tests/unit/test_app.py
@@ -1507,6 +1507,39 @@ def test_root_resource(auth_request):
     }
 
 
+def test_auth_response_with_usage_identifier_key(auth_request):
+    event = {
+        'type': 'TOKEN',
+        'authorizationToken': 'authtoken',
+        'methodArn': 'arn:aws:execute-api:us-west-2:1:id/dev/GET/a',
+    }
+    auth_app = app.Chalice('builtin-auth')
+
+    response = {
+        'context': {},
+        'principalId': 'principal',
+        'policyDocument': {
+            'Version': '2012-10-17',
+            'Statement': [
+                {'Action': 'execute-api:Invoke',
+                 'Effect': 'Allow',
+                 'Resource': [
+                     'arn:aws:execute-api:us-west-2:1:id/dev/*/a'
+                 ]}
+            ]
+        },
+        'usageIdentifierKey': 'api-key'
+    }
+
+    @auth_app.authorizer()
+    def builtin_auth(auth_request):
+        return app.AuthResponse(['/a'], 'principal',
+                                usage_identifier_key='api-key')
+
+    actual = builtin_auth(event, None)
+    assert actual == response
+
+
 def test_can_register_scheduled_event_with_str(sample_app):
     @sample_app.schedule('rate(1 minute)')
     def foo(event):