diff --git a/clang-tools-extra/clang-tidy/add_new_check.py b/clang-tools-extra/clang-tidy/add_new_check.py
--- a/clang-tools-extra/clang-tidy/add_new_check.py
+++ b/clang-tools-extra/clang-tidy/add_new_check.py
@@ -11,10 +11,16 @@
 from __future__ import print_function
 
 import argparse
+import io
 import os
 import re
 import sys
 
+# The documentation files are using UTF-8, however on Windows the default
+# encoding might be different (e.g. CP-1252). Force UTF-8 for all files.
+def open(*args, **kwargs):
+  kwargs.setdefault("encoding", "utf8")
+  return io.open(*args, **kwargs)
 
 # Adapts the module's CMakelist file. Returns 'True' if it could add a new
 # entry and 'False' if the entry already existed.
diff --git a/clang-tools-extra/clang-tidy/rename_check.py b/clang-tools-extra/clang-tidy/rename_check.py
--- a/clang-tools-extra/clang-tidy/rename_check.py
+++ b/clang-tools-extra/clang-tidy/rename_check.py
@@ -10,9 +10,15 @@
 
 import argparse
 import glob
+import io
 import os
 import re
 
+# The documentation files are using UTF-8, however on Windows the default
+# encoding might be different (e.g. CP-1252). Force UTF-8 for all files.
+def open(*args, **kwargs):
+  kwargs.setdefault("encoding", "utf8")
+  return io.open(*args, **kwargs)
 
 def replaceInFileRegex(fileName, sFrom, sTo):
   if sFrom == sTo: