diff --git a/tests/components/mqtt/conftest.py b/tests/components/mqtt/conftest.py
index ebe86c1f1df..91ece381f6d 100644
--- a/tests/components/mqtt/conftest.py
+++ b/tests/components/mqtt/conftest.py
@@ -1,5 +1,9 @@
 """Test fixtures for mqtt component."""
 
+from collections.abc import Generator
+from random import getrandbits
+from unittest.mock import patch
+
 import pytest
 
 from tests.components.light.conftest import mock_light_profiles  # noqa: F401
@@ -8,3 +12,20 @@ from tests.components.light.conftest import mock_light_profiles  # noqa: F401
 @pytest.fixture(autouse=True)
 def patch_hass_config(mock_hass_config: None) -> None:
     """Patch configuration.yaml."""
+
+
+@pytest.fixture
+def temp_dir_prefix() -> str:
+    """Set an alternate temp dir prefix."""
+    return "test"
+
+
+@pytest.fixture
+def mock_temp_dir(temp_dir_prefix: str) -> Generator[None, None, str]:
+    """Mock the certificate temp directory."""
+    with patch(
+        # Patch temp dir name to avoid tests fail running in parallel
+        "homeassistant.components.mqtt.util.TEMP_DIR_NAME",
+        f"home-assistant-mqtt-{temp_dir_prefix}-{getrandbits(10):03x}",
+    ) as mocked_temp_dir:
+        yield mocked_temp_dir
diff --git a/tests/components/mqtt/test_config_flow.py b/tests/components/mqtt/test_config_flow.py
index f0681a537da..c2a7e0065ce 100644
--- a/tests/components/mqtt/test_config_flow.py
+++ b/tests/components/mqtt/test_config_flow.py
@@ -2,7 +2,6 @@
 from collections.abc import Generator, Iterator
 from contextlib import contextmanager
 from pathlib import Path
-from random import getrandbits
 from ssl import SSLError
 from typing import Any
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -131,7 +130,9 @@ def mock_try_connection_time_out() -> Generator[MagicMock, None, None]:
 
 
 @pytest.fixture
-def mock_process_uploaded_file(tmp_path: Path) -> Generator[MagicMock, None, None]:
+def mock_process_uploaded_file(
+    tmp_path: Path, mock_temp_dir: str
+) -> Generator[MagicMock, None, None]:
     """Mock upload certificate files."""
     file_id_ca = str(uuid4())
     file_id_cert = str(uuid4())
@@ -159,11 +160,7 @@ def mock_process_uploaded_file(tmp_path: Path) -> Generator[MagicMock, None, Non
     with patch(
         "homeassistant.components.mqtt.config_flow.process_uploaded_file",
         side_effect=_mock_process_uploaded_file,
-    ) as mock_upload, patch(
-        # Patch temp dir name to avoid tests fail running in parallel
-        "homeassistant.components.mqtt.util.TEMP_DIR_NAME",
-        "home-assistant-mqtt" + f"-{getrandbits(10):03x}",
-    ):
+    ) as mock_upload:
         mock_upload.file_id = {
             mqtt.CONF_CERTIFICATE: file_id_ca,
             mqtt.CONF_CLIENT_CERT: file_id_cert,
diff --git a/tests/components/mqtt/test_util.py b/tests/components/mqtt/test_util.py
index e93a5e376bb..941072bc224 100644
--- a/tests/components/mqtt/test_util.py
+++ b/tests/components/mqtt/test_util.py
@@ -1,7 +1,9 @@
 """Test MQTT utils."""
 
 from collections.abc import Callable
+from pathlib import Path
 from random import getrandbits
+import tempfile
 from unittest.mock import patch
 
 import pytest
@@ -14,17 +16,6 @@ from tests.common import MockConfigEntry
 from tests.typing import MqttMockHAClient, MqttMockPahoClient
 
 
-@pytest.fixture(autouse=True)
-def mock_temp_dir():
-    """Mock the certificate temp directory."""
-    with patch(
-        # Patch temp dir name to avoid tests fail running in parallel
-        "homeassistant.components.mqtt.util.TEMP_DIR_NAME",
-        "home-assistant-mqtt" + f"-{getrandbits(10):03x}",
-    ) as mocked_temp_dir:
-        yield mocked_temp_dir
-
-
 @pytest.mark.parametrize(
     ("option", "content", "file_created"),
     [
@@ -34,31 +25,50 @@ def mock_temp_dir():
         (mqtt.CONF_CLIENT_KEY, "### PRIVATE KEY ###", True),
     ],
 )
+@pytest.mark.parametrize("temp_dir_prefix", ["create-test"])
 async def test_async_create_certificate_temp_files(
-    hass: HomeAssistant, mock_temp_dir, option, content, file_created
+    hass: HomeAssistant,
+    mock_temp_dir: str,
+    option: str,
+    content: str,
+    file_created: bool,
 ) -> None:
     """Test creating and reading and recovery certificate files."""
     config = {option: content}
-    await mqtt.util.async_create_certificate_temp_files(hass, config)
 
-    file_path = mqtt.util.get_file_path(option)
+    temp_dir = Path(tempfile.gettempdir()) / mock_temp_dir
+
+    # Create old file to be able to assert it is removed with auto option
+    def _ensure_old_file_exists() -> None:
+        if not temp_dir.exists():
+            temp_dir.mkdir(0o700)
+        temp_file = temp_dir / option
+        with open(temp_file, "wb") as old_file:
+            old_file.write(b"old content")
+            old_file.close()
+
+    await hass.async_add_executor_job(_ensure_old_file_exists)
+    await mqtt.util.async_create_certificate_temp_files(hass, config)
+    file_path = await hass.async_add_executor_job(mqtt.util.get_file_path, option)
     assert bool(file_path) is file_created
     assert (
-        mqtt.util.migrate_certificate_file_to_content(file_path or content) == content
+        await hass.async_add_executor_job(
+            mqtt.util.migrate_certificate_file_to_content, file_path or content
+        )
+        == content
     )
 
     # Make sure certificate temp files are recovered
-    if file_path:
-        # Overwrite content of file (except for auto option)
-        file = open(file_path, "wb")
-        file.write(b"invalid")
-        file.close()
+    await hass.async_add_executor_job(_ensure_old_file_exists)
 
     await mqtt.util.async_create_certificate_temp_files(hass, config)
-    file_path2 = mqtt.util.get_file_path(option)
+    file_path2 = await hass.async_add_executor_job(mqtt.util.get_file_path, option)
     assert bool(file_path2) is file_created
     assert (
-        mqtt.util.migrate_certificate_file_to_content(file_path2 or content) == content
+        await hass.async_add_executor_job(
+            mqtt.util.migrate_certificate_file_to_content, file_path2 or content
+        )
+        == content
     )
 
     assert file_path == file_path2
@@ -71,6 +81,26 @@ async def test_reading_non_exitisting_certificate_file() -> None:
     )
 
 
+@pytest.mark.parametrize("temp_dir_prefix", "unknown")
+async def test_return_default_get_file_path(
+    hass: HomeAssistant, mock_temp_dir: str
+) -> None:
+    """Test get_file_path returns default."""
+
+    def _get_file_path(file_path: Path) -> bool:
+        return (
+            not file_path.exists()
+            and mqtt.util.get_file_path("some_option", "mydefault") == "mydefault"
+        )
+
+    with patch(
+        "homeassistant.components.mqtt.util.TEMP_DIR_NAME",
+        f"home-assistant-mqtt-other-{getrandbits(10):03x}",
+    ) as mock_temp_dir:
+        tempdir = Path(tempfile.gettempdir()) / mock_temp_dir
+        assert await hass.async_add_executor_job(_get_file_path, tempdir)
+
+
 @patch("homeassistant.components.mqtt.PLATFORMS", [])
 async def test_waiting_for_client_not_loaded(
     hass: HomeAssistant,