diff --git a/Lib/idlelib/colorizer.py b/Lib/idlelib/colorizer.py
index b4df353012b788..247b0b186d6196 100644
--- a/Lib/idlelib/colorizer.py
+++ b/Lib/idlelib/colorizer.py
@@ -64,7 +64,7 @@ def make_pat():
 
 
 prog = make_pat()
-idprog = re.compile(r"\s+(\w+)")
+idprog = re.compile(r"\s+([^\\\s([:]+)")
 prog_group_name_to_tag = {
     "MATCH_SOFTKW": "KEYWORD",
     "CASE_SOFTKW": "KEYWORD",
@@ -346,8 +346,9 @@ def _add_tags_in_section(self, chars, head):
                 self._add_tag(a, b, head, name)
                 if matched_text in ("def", "class"):
                     if m1 := self.idprog.match(chars, b):
-                        a, b = m1.span(1)
-                        self._add_tag(a, b, head, "DEFINITION")
+                        if m1.groups()[0].isidentifier():
+                            a, b = m1.span(1)
+                            self._add_tag(a, b, head, "DEFINITION")
 
     def removecolors(self):
         "Remove all colorizing tags."
diff --git a/Lib/idlelib/idle_test/test_colorizer.py b/Lib/idlelib/idle_test/test_colorizer.py
index 308bc389384d33..d0c4957bfc6587 100644
--- a/Lib/idlelib/idle_test/test_colorizer.py
+++ b/Lib/idlelib/idle_test/test_colorizer.py
@@ -93,6 +93,14 @@ def test_idprog(self):
         self.assertIsNone(m)
         m = idprog.match(' space')
         self.assertEqual(m.group(0), ' space')
+        m = idprog.match('  space')
+        self.assertTrue(m.groups()[0].isidentifier())
+        m = idprog.match(' 42')
+        self.assertFalse(m.groups()[0].isidentifier())
+        m = idprog.match(' dot·[T]')
+        self.assertTrue(m.groups()[0].isidentifier())
+        m = idprog.match(' cls()')
+        self.assertTrue(m.groups()[0].isidentifier())
 
 
 class ColorConfigTest(unittest.TestCase):
diff --git a/Misc/NEWS.d/next/IDLE/2025-08-10-15-01-48.gh-issue-135052._pUw6u.rst b/Misc/NEWS.d/next/IDLE/2025-08-10-15-01-48.gh-issue-135052._pUw6u.rst
new file mode 100644
index 00000000000000..ceadf15edbad23
--- /dev/null
+++ b/Misc/NEWS.d/next/IDLE/2025-08-10-15-01-48.gh-issue-135052._pUw6u.rst
@@ -0,0 +1,2 @@
+Fix a bug that XID_Continue Unicode characters in function/class names
+highlighted incorrectly.