diff --git a/tests/conftest.py b/tests/conftest.py
index 7c46c04..ff8d071 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -26,6 +26,7 @@
 from uuid import uuid4
 
 import pytest
+from xdist import is_xdist_controller
 
 from cylc.flow import __version__ as CYLC_VERSION
 from cylc.flow.option_parsers import Options
@@ -376,12 +377,15 @@ def mod_test_dir(request, ses_test_dir):
     path = Path(ses_test_dir, request.module.__name__)
     path.mkdir(exist_ok=True)
     yield path
-    if _pytest_passed(request):
-        # test passed -> remove all files
-        rmtree(path, ignore_errors=False)
-    else:
-        # test failed -> remove the test dir if empty
-        _rm_if_empty(path)
+    # Only clean up if this is the xdist controller process:
+    if is_xdist_controller(request):
+        if _pytest_passed(request):
+            # test passed -> remove all files
+            rmtree(path, ignore_errors=False)
+
+        else:
+            # test failed -> remove the test dir if empty
+            _rm_if_empty(path)
 
 
 @pytest.fixture
@@ -390,12 +394,13 @@ def test_dir(request, mod_test_dir):
     path = Path(mod_test_dir, request.function.__name__)
     path.mkdir(parents=True, exist_ok=True)
     yield path
-    if _pytest_passed(request):
-        # test passed -> remove all files
-        rmtree(path, ignore_errors=False)
-    else:
-        # test failed -> remove the test dir if empty
-        _rm_if_empty(path)
+    if is_xdist_controller(request):
+        if _pytest_passed(request):
+            # test passed -> remove all files
+            rmtree(path, ignore_errors=False)
+        else:
+            # test failed -> remove the test dir if empty
+            _rm_if_empty(path)
 
 
 @pytest.fixture
diff --git a/tests/functional/test_reinstall.py b/tests/functional/test_reinstall.py
index 7c7b06b..4fae2fa 100644
--- a/tests/functional/test_reinstall.py
+++ b/tests/functional/test_reinstall.py
@@ -37,6 +37,7 @@
 from cylc.flow.install import reinstall_workflow
 from cylc.flow.pathutil import get_workflow_run_dir
 import pytest
+from xdist import is_xdist_controller
 
 from cylc.rose.utilities import (
     ROSE_ORIG_HOST_INSTALLED_OVERRIDE_STRING as ROHIOS,
@@ -72,7 +73,7 @@ def fixture_provide_flow(tmp_path_factory, request):
         'flowpath': flowpath,
         'srcpath': srcpath
     }
-    if not request.session.testsfailed:
+    if is_xdist_controller(request) and not request.session.testsfailed:
         shutil.rmtree(srcpath)
         shutil.rmtree(flowpath)
 
diff --git a/tests/functional/test_reinstall_clean.py b/tests/functional/test_reinstall_clean.py
index e42617b..47879d1 100644
--- a/tests/functional/test_reinstall_clean.py
+++ b/tests/functional/test_reinstall_clean.py
@@ -35,6 +35,7 @@
 from cylc.flow.hostuserutil import get_host
 from cylc.flow.pathutil import get_workflow_run_dir
 import pytest
+from xdist import is_xdist_controller
 
 from cylc.rose.utilities import (
     ROSE_ORIG_HOST_INSTALLED_OVERRIDE_STRING as ROHIOS,
@@ -70,7 +71,10 @@ def fixture_provide_flow(tmp_path_factory, request):
         'flowpath': flowpath,
         'srcpath': srcpath
     }
-    if not request.session.testsfailed:
+    if (
+        is_xdist_controller(request)
+        and not request.session.testsfailed
+    ):
         shutil.rmtree(srcpath)
         shutil.rmtree(flowpath)