diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 606f48d..8f2c59a 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -367,6 +367,28 @@
   return results
 
 
+def _CheckLibcxxRevision(input_api, output_api):
+  """Makes sure that libcxx_revision is set correctly."""
+  if 'DEPS' not in [f.LocalPath() for f in input_api.AffectedFiles()]:
+    return []
+
+  script_path = input_api.os_path.join('testing', 'tools', 'libcxx_check.py')
+  buildtools_deps_path = input_api.os_path.join('buildtools',
+                                                'deps_revisions.gni')
+
+  try:
+    errors = input_api.subprocess.check_output(
+        [script_path, 'DEPS', buildtools_deps_path])
+  except input_api.subprocess.CalledProcessError as error:
+    msg = 'libcxx_check.py failed:'
+    long_text = error.output.decode('utf-8', 'ignore')
+    return [output_api.PresubmitError(msg, long_text=long_text)]
+
+  if errors:
+    return [output_api.PresubmitError(errors)]
+  return []
+
+
 def _CheckTestDuplicates(input_api, output_api):
   """Checks that pixel and javascript tests don't contain duplicates.
   We use .in and .pdf files, having both can cause race conditions on the bots,
@@ -474,6 +496,7 @@
       input_api.canned_checks.CheckChangeLintsClean(
           input_api, output_api, lint_filters=LINT_FILTERS))
   results.extend(_CheckIncludeOrder(input_api, output_api))
+  results.extend(_CheckLibcxxRevision(input_api, output_api))
   results.extend(_CheckTestDuplicates(input_api, output_api))
   results.extend(_CheckPNGFormat(input_api, output_api))
   results.extend(_CheckUselessForwardDeclarations(input_api, output_api))
diff --git a/testing/tools/libcxx_check.py b/testing/tools/libcxx_check.py
new file mode 100755
index 0000000..ad6abea
--- /dev/null
+++ b/testing/tools/libcxx_check.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+# Copyright 2022 The PDFium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Verifies libcxx_revision entries are in sync.
+
+DEPS and buildtools/deps_revisions.gni both have libcxx_revision entries.
+Check that they are in sync.
+"""
+
+import re
+import sys
+
+
+def _ExtractRevisionFromFile(path, regex):
+  """Gets the revision by reading path and searching the lines using regex."""
+  data = open(path, 'rb').read().splitlines()
+  revision = None
+  for line in data:
+    match = regex.match(line)
+    if not match:
+      continue
+    if revision:
+      return None
+    revision = match.group(1)
+  return revision
+
+
+def _GetDepsLibcxxRevision(deps_path):
+  """Gets the libcxx_revision from DEPS."""
+  regex = re.compile(b"^  'libcxx_revision': '(.*)',$")
+  return _ExtractRevisionFromFile(deps_path, regex)
+
+
+def _GetBuildtoolsLibcxxRevision(buildtools_deps_path):
+  """Gets the libcxx_revision from buildtools/deps_revisions.gni."""
+  regex = re.compile(b'^  libcxx_revision = "(.*)"$')
+  return _ExtractRevisionFromFile(buildtools_deps_path, regex)
+
+
+def main():
+  if len(sys.argv) != 3:
+    print('Wrong number of arguments')
+    return 0
+
+  deps_path = sys.argv[1]
+  deps_revision = _GetDepsLibcxxRevision(deps_path)
+  if not deps_revision:
+    print('Cannot parse', deps_path)
+    return 0
+
+  buildtools_deps_path = sys.argv[2]
+  buildtools_revision = _GetBuildtoolsLibcxxRevision(buildtools_deps_path)
+  if not buildtools_revision:
+    print('Cannot parse', buildtools_deps_path)
+    return 0
+
+  if deps_revision != buildtools_revision:
+    print('libcxx_revision mismatch between %s and %s: %s vs. %s' %
+          (deps_path, buildtools_deps_path, deps_revision, buildtools_revision))
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())