diff --git a/.changeset/four-taxis-fry.md b/.changeset/four-taxis-fry.md
new file mode 100644
index 00000000000..f12ce03f64a
--- /dev/null
+++ b/.changeset/four-taxis-fry.md
@@ -0,0 +1,7 @@
+---
+'@firebase/app-check': patch
+'@firebase/app-check-types': patch
+'firebase': patch
+---
+
+Fixed argument typings for `activate()`.
diff --git a/packages/app-check-types/index.d.ts b/packages/app-check-types/index.d.ts
index b91ac5ac820..e75208c7c7b 100644
--- a/packages/app-check-types/index.d.ts
+++ b/packages/app-check-types/index.d.ts
@@ -32,7 +32,11 @@ export interface FirebaseAppCheck {
    * defaults to false and can be set in the app config.
    */
   activate(
-    siteKeyOrProvider: string | AppCheckProvider,
+    siteKeyOrProvider:
+      | string
+      | AppCheckProvider
+      | CustomProvider
+      | ReCaptchaV3Provider,
     isTokenAutoRefreshEnabled?: boolean
   ): void;
 
diff --git a/packages/app-check/src/factory.ts b/packages/app-check/src/factory.ts
index 8c0995afbcc..18832eadc8e 100644
--- a/packages/app-check/src/factory.ts
+++ b/packages/app-check/src/factory.ts
@@ -18,7 +18,9 @@
 import {
   FirebaseAppCheck,
   AppCheckProvider,
-  AppCheckTokenResult
+  AppCheckTokenResult,
+  ReCaptchaV3Provider,
+  CustomProvider
 } from '@firebase/app-check-types';
 import {
   activate,
@@ -33,6 +35,10 @@ import {
   addTokenListener,
   removeTokenListener
 } from './internal-api';
+import {
+  ReCaptchaV3Provider as ReCaptchaV3ProviderImpl,
+  CustomProvider as CustomProviderImpl
+} from './providers';
 import { Provider } from '@firebase/component';
 import { PartialObserver } from '@firebase/util';
 
@@ -46,12 +52,23 @@ export function factory(
   return {
     app,
     activate: (
-      siteKeyOrProvider: AppCheckProvider | string,
+      siteKeyOrProvider:
+        | ReCaptchaV3Provider
+        | CustomProvider
+        | AppCheckProvider
+        | string,
       isTokenAutoRefreshEnabled?: boolean
     ) =>
       activate(
         app,
-        siteKeyOrProvider,
+        // Public types of ReCaptchaV3Provider/CustomProvider don't
+        // expose getToken() and aren't recognized as the internal
+        // class version of themselves.
+        siteKeyOrProvider as
+          | ReCaptchaV3ProviderImpl
+          | CustomProviderImpl
+          | AppCheckProvider
+          | string,
         platformLoggerProvider,
         isTokenAutoRefreshEnabled
       ),
diff --git a/packages/firebase/index.d.ts b/packages/firebase/index.d.ts
index e7580ac6ac8..71902a5c9b6 100644
--- a/packages/firebase/index.d.ts
+++ b/packages/firebase/index.d.ts
@@ -1580,14 +1580,18 @@ declare namespace firebase.appCheck {
   export interface AppCheck {
     /**
      * Activate AppCheck
-     * @param provider reCAPTCHA or custom token provider.
+     * @param provider reCAPTCHA provider, custom token provider, or reCAPTCHA site key.
      * @param isTokenAutoRefreshEnabled If true, the SDK automatically
      * refreshes App Check tokens as needed. If undefined, defaults to the
      * value of `app.automaticDataCollectionEnabled`, which defaults to
      * false and can be set in the app config.
      */
     activate(
-      provider: AppCheckProvider,
+      provider:
+        | ReCaptchaV3Provider
+        | CustomProvider
+        | AppCheckProvider
+        | string,
       isTokenAutoRefreshEnabled?: boolean
     ): void;