diff --git a/pandas/tests/io/test_compression.py b/pandas/tests/io/test_compression.py
index 9bdfbad347481..af83ec4a55fa5 100644
--- a/pandas/tests/io/test_compression.py
+++ b/pandas/tests/io/test_compression.py
@@ -202,6 +202,7 @@ def test_gzip_reproducibility_file_object():
     assert output == buffer.getvalue()
 
 
+@pytest.mark.single_cpu
 def test_with_missing_lzma():
     """Tests if import pandas works when lzma is not present."""
     # https://github.com/pandas-dev/pandas/issues/27575
@@ -215,6 +216,7 @@ def test_with_missing_lzma():
     subprocess.check_output([sys.executable, "-c", code], stderr=subprocess.PIPE)
 
 
+@pytest.mark.single_cpu
 def test_with_missing_lzma_runtime():
     """Tests if RuntimeError is hit when calling lzma without
     having the module available.
diff --git a/pandas/tests/plotting/test_converter.py b/pandas/tests/plotting/test_converter.py
index 6caeb3a5d7445..cadd4c4589964 100644
--- a/pandas/tests/plotting/test_converter.py
+++ b/pandas/tests/plotting/test_converter.py
@@ -43,6 +43,7 @@
 dates = pytest.importorskip("matplotlib.dates")
 
 
+@pytest.mark.single_cpu
 def test_registry_mpl_resets():
     # Check that Matplotlib converters are properly reset (see issue #27481)
     code = (
@@ -63,6 +64,7 @@ def test_timtetonum_accepts_unicode():
 
 
 class TestRegistration:
+    @pytest.mark.single_cpu
     def test_dont_register_by_default(self):
         # Run in subprocess to ensure a clean state
         code = (
diff --git a/pandas/tests/test_common.py b/pandas/tests/test_common.py
index 4860ee235c03d..fa7750397369b 100644
--- a/pandas/tests/test_common.py
+++ b/pandas/tests/test_common.py
@@ -233,6 +233,7 @@ def test_temp_setattr(with_exception):
     assert ser.name == "first"
 
 
+@pytest.mark.single_cpu
 def test_str_size():
     # GH#21758
     a = "a"
diff --git a/pandas/tests/test_downstream.py b/pandas/tests/test_downstream.py
index 7354e313e24f4..09594588be81c 100644
--- a/pandas/tests/test_downstream.py
+++ b/pandas/tests/test_downstream.py
@@ -119,11 +119,13 @@ def test_xarray_cftimeindex_nearest():
     assert result == expected
 
 
+@pytest.mark.single_cpu
 def test_oo_optimizable():
     # GH 21071
     subprocess.check_call([sys.executable, "-OO", "-c", "import pandas"])
 
 
+@pytest.mark.single_cpu
 def test_oo_optimized_datetime_index_unpickle():
     # GH 42866
     subprocess.check_call(
@@ -200,6 +202,7 @@ def test_yaml_dump(df):
     tm.assert_frame_equal(df, loaded2)
 
 
+@pytest.mark.single_cpu
 def test_missing_required_dependency():
     # GH 23868
     # To ensure proper isolation, we pass these flags