diff --git a/src/google/adk/auth/auth_credential.py b/src/google/adk/auth/auth_credential.py
index 6e4f73351f..e205d9be52 100644
--- a/src/google/adk/auth/auth_credential.py
+++ b/src/google/adk/auth/auth_credential.py
@@ -79,6 +79,7 @@ class OAuth2Auth(BaseModelWithConfig):
   auth_code: Optional[str] = None
   access_token: Optional[str] = None
   refresh_token: Optional[str] = None
+  id_token: Optional[str] = None
   expires_at: Optional[int] = None
   expires_in: Optional[int] = None
   audience: Optional[str] = None
diff --git a/src/google/adk/auth/oauth2_credential_util.py b/src/google/adk/auth/oauth2_credential_util.py
index d2f40b339f..888c8d0d39 100644
--- a/src/google/adk/auth/oauth2_credential_util.py
+++ b/src/google/adk/auth/oauth2_credential_util.py
@@ -107,11 +107,13 @@ def update_credential_with_tokens(
       auth_credential: The authentication credential to update.
       tokens: The OAuth2Token object containing new token information.
   """
-  auth_credential.oauth2.access_token = tokens.get("access_token")
-  auth_credential.oauth2.refresh_token = tokens.get("refresh_token")
-  auth_credential.oauth2.expires_at = (
-      int(tokens.get("expires_at")) if tokens.get("expires_at") else None
-  )
-  auth_credential.oauth2.expires_in = (
-      int(tokens.get("expires_in")) if tokens.get("expires_in") else None
-  )
+  if auth_credential.oauth2:
+    auth_credential.oauth2.access_token = tokens.get("access_token")
+    auth_credential.oauth2.refresh_token = tokens.get("refresh_token")
+    auth_credential.oauth2.id_token = tokens.get("id_token")
+    auth_credential.oauth2.expires_at = (
+        int(tokens.get("expires_at")) if tokens.get("expires_at") else None
+    )
+    auth_credential.oauth2.expires_in = (
+        int(tokens.get("expires_in")) if tokens.get("expires_in") else None
+    )
diff --git a/tests/unittests/auth/test_oauth2_credential_util.py b/tests/unittests/auth/test_oauth2_credential_util.py
index 1e499ca741..88398c482a 100644
--- a/tests/unittests/auth/test_oauth2_credential_util.py
+++ b/tests/unittests/auth/test_oauth2_credential_util.py
@@ -222,6 +222,7 @@ def test_update_credential_with_tokens(self):
     tokens = OAuth2Token({
         "access_token": "new_access_token",
         "refresh_token": "new_refresh_token",
+        "id_token": "new_id_token",
         "expires_at": expected_expires_at,
         "expires_in": 3600,
     })
@@ -230,5 +231,16 @@ def test_update_credential_with_tokens(self):
 
     assert credential.oauth2.access_token == "new_access_token"
     assert credential.oauth2.refresh_token == "new_refresh_token"
+    assert credential.oauth2.id_token == "new_id_token"
     assert credential.oauth2.expires_at == expected_expires_at
     assert credential.oauth2.expires_in == 3600
+
+  def test_update_credential_with_tokens_none(self) -> None:
+    credential = AuthCredential(
+        auth_type=AuthCredentialTypes.API_KEY,
+    )
+    tokens = OAuth2Token({"access_token": "new_access_token"})
+
+    # Should not raise any exceptions when oauth2 is None
+    update_credential_with_tokens(credential, tokens)
+    assert credential.oauth2 is None