diff --git a/homeassistant/components/google_pubsub/__init__.py b/homeassistant/components/google_pubsub/__init__.py
index 19530d9d663..d583bc5aac0 100644
--- a/homeassistant/components/google_pubsub/__init__.py
+++ b/homeassistant/components/google_pubsub/__init__.py
@@ -41,16 +41,10 @@ CONFIG_SCHEMA = vol.Schema(
 
 def setup(hass: HomeAssistant, yaml_config: dict[str, Any]):
     """Activate Google Pub/Sub component."""
-
     config = yaml_config[DOMAIN]
     project_id = config[CONF_PROJECT_ID]
     topic_name = config[CONF_TOPIC_NAME]
-    if hass.config.config_dir:
-        service_principal_path = os.path.join(
-            hass.config.config_dir, config[CONF_SERVICE_PRINCIPAL]
-        )
-    else:
-        service_principal_path = config[CONF_SERVICE_PRINCIPAL]
+    service_principal_path = hass.config.path(config[CONF_SERVICE_PRINCIPAL])
 
     if not os.path.isfile(service_principal_path):
         _LOGGER.error("Path to credentials file cannot be found")
diff --git a/tests/components/google_pubsub/test_init.py b/tests/components/google_pubsub/test_init.py
index fc1fecb04ed..d31d28e7302 100644
--- a/tests/components/google_pubsub/test_init.py
+++ b/tests/components/google_pubsub/test_init.py
@@ -1,6 +1,7 @@
 """The tests for the Google Pub/Sub component."""
 from dataclasses import dataclass
 from datetime import datetime
+import os
 import unittest.mock as mock
 
 import pytest
@@ -51,13 +52,12 @@ def mock_client_fixture():
         yield client
 
 
-@pytest.fixture(autouse=True, name="mock_os")
-def mock_os_fixture():
-    """Mock the OS cli."""
-    with mock.patch(f"{GOOGLE_PUBSUB_PATH}.os") as os_cli:
-        os_cli.path = mock.MagicMock()
-        setattr(os_cli.path, "join", mock.MagicMock(return_value="path"))
-        yield os_cli
+@pytest.fixture(autouse=True, name="mock_is_file")
+def mock_is_file_fixture():
+    """Mock os.path.isfile."""
+    with mock.patch(f"{GOOGLE_PUBSUB_PATH}.os.path.isfile") as is_file:
+        is_file.return_value = True
+        yield is_file
 
 
 @pytest.fixture(autouse=True)
@@ -84,9 +84,9 @@ async def test_minimal_config(hass, mock_client):
     assert hass.bus.listen.called
     assert hass.bus.listen.call_args_list[0][0][0] == EVENT_STATE_CHANGED
     assert mock_client.PublisherClient.from_service_account_json.call_count == 1
-    assert (
-        mock_client.PublisherClient.from_service_account_json.call_args[0][0] == "path"
-    )
+    assert mock_client.PublisherClient.from_service_account_json.call_args[0][
+        0
+    ] == os.path.join(hass.config.config_dir, "creds")
 
 
 async def test_full_config(hass, mock_client):
@@ -111,9 +111,9 @@ async def test_full_config(hass, mock_client):
     assert hass.bus.listen.called
     assert hass.bus.listen.call_args_list[0][0][0] == EVENT_STATE_CHANGED
     assert mock_client.PublisherClient.from_service_account_json.call_count == 1
-    assert (
-        mock_client.PublisherClient.from_service_account_json.call_args[0][0] == "path"
-    )
+    assert mock_client.PublisherClient.from_service_account_json.call_args[0][
+        0
+    ] == os.path.join(hass.config.config_dir, "creds")
 
 
 def make_event(entity_id):