diff --git a/changelog/13420.bugfix.rst b/changelog/13420.bugfix.rst
new file mode 100644
index 00000000000..02f7372a759
--- /dev/null
+++ b/changelog/13420.bugfix.rst
@@ -0,0 +1 @@
+Added ``lru_cache`` to ``nodes._check_initialpaths_for_relpath``.
diff --git a/src/_pytest/nodes.py b/src/_pytest/nodes.py
index 51bc5174628..2b818ade252 100644
--- a/src/_pytest/nodes.py
+++ b/src/_pytest/nodes.py
@@ -3,6 +3,7 @@
 
 import abc
 from functools import cached_property
+from functools import lru_cache
 from inspect import signature
 import os
 import pathlib
@@ -543,8 +544,11 @@ def _traceback_filter(self, excinfo: ExceptionInfo[BaseException]) -> Traceback:
         return excinfo.traceback
 
 
-def _check_initialpaths_for_relpath(session: Session, path: Path) -> str | None:
-    for initial_path in session._initialpaths:
+@lru_cache(maxsize=1000)
+def _check_initialpaths_for_relpath(
+    initial_paths: frozenset[Path], path: Path
+) -> str | None:
+    for initial_path in initial_paths:
         if commonpath(path, initial_path) == initial_path:
             rel = str(path.relative_to(initial_path))
             return "" if rel == "." else rel
@@ -594,7 +598,7 @@ def __init__(
             try:
                 nodeid = str(self.path.relative_to(session.config.rootpath))
             except ValueError:
-                nodeid = _check_initialpaths_for_relpath(session, path)
+                nodeid = _check_initialpaths_for_relpath(session._initialpaths, path)
 
             if nodeid and os.sep != SEP:
                 nodeid = nodeid.replace(os.sep, SEP)
diff --git a/testing/test_nodes.py b/testing/test_nodes.py
index f039acf243b..f5f21e9775c 100644
--- a/testing/test_nodes.py
+++ b/testing/test_nodes.py
@@ -3,7 +3,6 @@
 
 from pathlib import Path
 import re
-from typing import cast
 import warnings
 
 from _pytest import nodes
@@ -103,24 +102,15 @@ def test__check_initialpaths_for_relpath() -> None:
     """Ensure that it handles dirs, and does not always use dirname."""
     cwd = Path.cwd()
 
-    class FakeSession1:
-        _initialpaths = frozenset({cwd})
+    initial_paths = frozenset({cwd})
 
-    session = cast(pytest.Session, FakeSession1)
-
-    assert nodes._check_initialpaths_for_relpath(session, cwd) == ""
+    assert nodes._check_initialpaths_for_relpath(initial_paths, cwd) == ""
 
     sub = cwd / "file"
-
-    class FakeSession2:
-        _initialpaths = frozenset({cwd})
-
-    session = cast(pytest.Session, FakeSession2)
-
-    assert nodes._check_initialpaths_for_relpath(session, sub) == "file"
+    assert nodes._check_initialpaths_for_relpath(initial_paths, sub) == "file"
 
     outside = Path("/outside-this-does-not-exist")
-    assert nodes._check_initialpaths_for_relpath(session, outside) is None
+    assert nodes._check_initialpaths_for_relpath(initial_paths, outside) is None
 
 
 def test_failure_with_changed_cwd(pytester: Pytester) -> None: