diff --git a/google/cloud/iam_credentials_v1/services/iam_credentials/client.py b/google/cloud/iam_credentials_v1/services/iam_credentials/client.py
index ad4b498..39db062 100644
--- a/google/cloud/iam_credentials_v1/services/iam_credentials/client.py
+++ b/google/cloud/iam_credentials_v1/services/iam_credentials/client.py
@@ -355,6 +355,10 @@ def __init__(
                 client_cert_source_for_mtls=client_cert_source_func,
                 quota_project_id=client_options.quota_project_id,
                 client_info=client_info,
+                always_use_jwt_access=(
+                    Transport == type(self).get_transport_class("grpc")
+                    or Transport == type(self).get_transport_class("grpc_asyncio")
+                ),
             )
 
     def generate_access_token(
diff --git a/tests/unit/gapic/credentials_v1/test_iam_credentials.py b/tests/unit/gapic/credentials_v1/test_iam_credentials.py
index 8d8ef1d..009d48e 100644
--- a/tests/unit/gapic/credentials_v1/test_iam_credentials.py
+++ b/tests/unit/gapic/credentials_v1/test_iam_credentials.py
@@ -123,18 +123,6 @@ def test_iam_credentials_client_from_service_account_info(client_class):
         assert client.transport._host == "iamcredentials.googleapis.com:443"
 
 
-@pytest.mark.parametrize(
-    "client_class", [IAMCredentialsClient, IAMCredentialsAsyncClient,]
-)
-def test_iam_credentials_client_service_account_always_use_jwt(client_class):
-    with mock.patch.object(
-        service_account.Credentials, "with_always_use_jwt_access", create=True
-    ) as use_jwt:
-        creds = service_account.Credentials(None, None, None)
-        client = client_class(credentials=creds)
-        use_jwt.assert_not_called()
-
-
 @pytest.mark.parametrize(
     "transport_class,transport_name",
     [
@@ -142,7 +130,7 @@ def test_iam_credentials_client_service_account_always_use_jwt(client_class):
         (transports.IAMCredentialsGrpcAsyncIOTransport, "grpc_asyncio"),
     ],
 )
-def test_iam_credentials_client_service_account_always_use_jwt_true(
+def test_iam_credentials_client_service_account_always_use_jwt(
     transport_class, transport_name
 ):
     with mock.patch.object(
@@ -152,6 +140,13 @@ def test_iam_credentials_client_service_account_always_use_jwt_true(
         transport = transport_class(credentials=creds, always_use_jwt_access=True)
         use_jwt.assert_called_once_with(True)
 
+    with mock.patch.object(
+        service_account.Credentials, "with_always_use_jwt_access", create=True
+    ) as use_jwt:
+        creds = service_account.Credentials(None, None, None)
+        transport = transport_class(credentials=creds, always_use_jwt_access=False)
+        use_jwt.assert_not_called()
+
 
 @pytest.mark.parametrize(
     "client_class", [IAMCredentialsClient, IAMCredentialsAsyncClient,]
@@ -232,6 +227,7 @@ def test_iam_credentials_client_client_options(
             client_cert_source_for_mtls=None,
             quota_project_id=None,
             client_info=transports.base.DEFAULT_CLIENT_INFO,
+            always_use_jwt_access=True,
         )
 
     # Check the case api_endpoint is not provided and GOOGLE_API_USE_MTLS_ENDPOINT is
@@ -248,6 +244,7 @@ def test_iam_credentials_client_client_options(
                 client_cert_source_for_mtls=None,
                 quota_project_id=None,
                 client_info=transports.base.DEFAULT_CLIENT_INFO,
+                always_use_jwt_access=True,
             )
 
     # Check the case api_endpoint is not provided and GOOGLE_API_USE_MTLS_ENDPOINT is
@@ -264,6 +261,7 @@ def test_iam_credentials_client_client_options(
                 client_cert_source_for_mtls=None,
                 quota_project_id=None,
                 client_info=transports.base.DEFAULT_CLIENT_INFO,
+                always_use_jwt_access=True,
             )
 
     # Check the case api_endpoint is not provided and GOOGLE_API_USE_MTLS_ENDPOINT has
@@ -292,6 +290,7 @@ def test_iam_credentials_client_client_options(
             client_cert_source_for_mtls=None,
             quota_project_id="octopus",
             client_info=transports.base.DEFAULT_CLIENT_INFO,
+            always_use_jwt_access=True,
         )
 
 
@@ -358,6 +357,7 @@ def test_iam_credentials_client_mtls_env_auto(
                 client_cert_source_for_mtls=expected_client_cert_source,
                 quota_project_id=None,
                 client_info=transports.base.DEFAULT_CLIENT_INFO,
+                always_use_jwt_access=True,
             )
 
     # Check the case ADC client cert is provided. Whether client cert is used depends on
@@ -391,6 +391,7 @@ def test_iam_credentials_client_mtls_env_auto(
                         client_cert_source_for_mtls=expected_client_cert_source,
                         quota_project_id=None,
                         client_info=transports.base.DEFAULT_CLIENT_INFO,
+                        always_use_jwt_access=True,
                     )
 
     # Check the case client_cert_source and ADC client cert are not provided.
@@ -412,6 +413,7 @@ def test_iam_credentials_client_mtls_env_auto(
                     client_cert_source_for_mtls=None,
                     quota_project_id=None,
                     client_info=transports.base.DEFAULT_CLIENT_INFO,
+                    always_use_jwt_access=True,
                 )
 
 
@@ -442,6 +444,7 @@ def test_iam_credentials_client_client_options_scopes(
             client_cert_source_for_mtls=None,
             quota_project_id=None,
             client_info=transports.base.DEFAULT_CLIENT_INFO,
+            always_use_jwt_access=True,
         )
 
 
@@ -472,6 +475,7 @@ def test_iam_credentials_client_client_options_credentials_file(
             client_cert_source_for_mtls=None,
             quota_project_id=None,
             client_info=transports.base.DEFAULT_CLIENT_INFO,
+            always_use_jwt_access=True,
         )
 
 
@@ -491,6 +495,7 @@ def test_iam_credentials_client_client_options_from_dict():
             client_cert_source_for_mtls=None,
             quota_project_id=None,
             client_info=transports.base.DEFAULT_CLIENT_INFO,
+            always_use_jwt_access=True,
         )