diff --git a/Lib/lib2to3/refactor.py b/Lib/lib2to3/refactor.py
index 7841b99a5cd4c1..475814eeb93fd7 100644
--- a/Lib/lib2to3/refactor.py
+++ b/Lib/lib2to3/refactor.py
@@ -287,8 +287,11 @@ def refactor_dir(self, dir_name, write=False, doctests_only=False):
         Python files are assumed to have a .py extension.
 
         Files and subdirectories starting with '.' are skipped.
+
+        Returns a list of changed files.
         """
         py_ext = os.extsep + "py"
+        changed = []
         for dirpath, dirnames, filenames in os.walk(dir_name):
             self.log_debug("Descending into %s", dirpath)
             dirnames.sort()
@@ -297,9 +300,11 @@ def refactor_dir(self, dir_name, write=False, doctests_only=False):
                 if (not name.startswith(".") and
                     os.path.splitext(name)[1] == py_ext):
                     fullname = os.path.join(dirpath, name)
-                    self.refactor_file(fullname, write, doctests_only)
+                    if self.refactor_file(fullname, write, doctests_only):
+                        changed.append(fullname)
             # Modify dirnames in-place to remove subdirs with leading dots
             dirnames[:] = [dn for dn in dirnames if not dn.startswith(".")]
+        return changed
 
     def _read_python_source(self, filename):
         """
@@ -318,27 +323,37 @@ def _read_python_source(self, filename):
             return f.read(), encoding
 
     def refactor_file(self, filename, write=False, doctests_only=False):
-        """Refactors a file."""
+        """Refactors a file.
+
+        Returns:
+          True: if the file was modified.
+          False: if the file was not modified.
+          None: if the file could not be read.
+        """
         input, encoding = self._read_python_source(filename)
         if input is None:
             # Reading the file failed.
-            return
+            return None
         input += "\n" # Silence certain parse errors
         if doctests_only:
             self.log_debug("Refactoring doctests in %s", filename)
             output = self.refactor_docstring(input, filename)
             if self.write_unchanged_files or output != input:
                 self.processed_file(output, filename, input, write, encoding)
+                return True
             else:
                 self.log_debug("No doctest changes in %s", filename)
+                return False
         else:
             tree = self.refactor_string(input, filename)
             if self.write_unchanged_files or (tree and tree.was_changed):
                 # The [:-1] is to take off the \n we added earlier
                 self.processed_file(str(tree)[:-1], filename,
                                     write=write, encoding=encoding)
+                return True
             else:
                 self.log_debug("No changes in %s", filename)
+                return False
 
     def refactor_string(self, data, name):
         """Refactor a given input string.
diff --git a/Lib/lib2to3/tests/test_refactor.py b/Lib/lib2to3/tests/test_refactor.py
index 9e3b8fbb90b2f3..35b19658b97f2f 100644
--- a/Lib/lib2to3/tests/test_refactor.py
+++ b/Lib/lib2to3/tests/test_refactor.py
@@ -179,7 +179,7 @@ def print_output(self, old_text, new_text, filename, equal):
 
     def check_file_refactoring(self, test_file, fixers=_2TO3_FIXERS,
                                options=None, mock_log_debug=None,
-                               actually_write=True):
+                               actually_write=True, expected_return=True):
         test_file = self.init_test_file(test_file)
         old_contents = self.read_file(test_file)
         rt = self.rt(fixers=fixers, options=options)
@@ -191,9 +191,13 @@ def check_file_refactoring(self, test_file, fixers=_2TO3_FIXERS,
 
         if not actually_write:
             return
-        rt.refactor_file(test_file, True)
+        ret = rt.refactor_file(test_file, True)
         new_contents = self.read_file(test_file)
-        self.assertNotEqual(old_contents, new_contents)
+        write_unchanged = options and options.get(
+            "write_unchanged_files", False)
+        if expected_return and not write_unchanged:
+            self.assertNotEqual(old_contents, new_contents)
+        self.assertEqual(ret, expected_return)
         return new_contents
 
     def init_test_file(self, test_file):
@@ -220,6 +224,14 @@ def test_refactor_file(self):
         test_file = os.path.join(FIXER_DIR, "parrot_example.py")
         self.check_file_refactoring(test_file, _DEFAULT_FIXERS)
 
+    def test_refactor_file_return_false(self):
+        test_file = os.path.join(FIXER_DIR, "parrot_example.py")
+        self.check_file_refactoring(test_file, fixers=(), expected_return=False)
+
+    def test_refactor_file_return_true(self):
+        test_file = os.path.join(TEST_DATA_DIR, "different_encoding.py")
+        self.check_file_refactoring(test_file, expected_return=True)
+
     def test_refactor_file_write_unchanged_file(self):
         test_file = os.path.join(FIXER_DIR, "parrot_example.py")
         debug_messages = []
@@ -241,9 +253,11 @@ def recording_log_debug(msg, *args):
             self.fail("%r not matched in %r" % (message_regex, debug_messages))
 
     def test_refactor_dir(self):
-        def check(structure, expected):
+        files_to_refactor = {"stuff.py"}
+        def check(structure, expected, expected_return):
             def mock_refactor_file(self, f, *args):
                 got.append(f)
+                return os.path.basename(f) in files_to_refactor
             save_func = refactor.RefactoringTool.refactor_file
             refactor.RefactoringTool.refactor_file = mock_refactor_file
             rt = self.rt()
@@ -253,13 +267,17 @@ def mock_refactor_file(self, f, *args):
                 os.mkdir(os.path.join(dir, "a_dir"))
                 for fn in structure:
                     open(os.path.join(dir, fn), "wb").close()
-                rt.refactor_dir(dir)
+                ret =rt.refactor_dir(dir)
+                # Just check the basenames since we are working with tempdirs
+                self.assertEqual(
+                    list(map(os.path.basename, ret)),
+                    expected_return)
             finally:
                 refactor.RefactoringTool.refactor_file = save_func
                 shutil.rmtree(dir)
             self.assertEqual(got,
                              [os.path.join(dir, path) for path in expected])
-        check([], [])
+        check([], [], [])
         tree = ["nothing",
                 "hi.py",
                 ".dumb",
@@ -267,10 +285,11 @@ def mock_refactor_file(self, f, *args):
                 "notpy.npy",
                 "sappy"]
         expected = ["hi.py"]
-        check(tree, expected)
+        check(tree, expected, [])
         tree = ["hi.py",
                 os.path.join("a_dir", "stuff.py")]
-        check(tree, tree)
+        # stuff.py returns True from refactor_file and so is in expected_return
+        check(tree, tree, ["stuff.py"])
 
     def test_file_encoding(self):
         fn = os.path.join(TEST_DATA_DIR, "different_encoding.py")
diff --git a/Misc/NEWS.d/next/Library/2018-11-20-14-31-36.bpo-35282.uimIBv.rst b/Misc/NEWS.d/next/Library/2018-11-20-14-31-36.bpo-35282.uimIBv.rst
new file mode 100644
index 00000000000000..4888112cb76fe7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-11-20-14-31-36.bpo-35282.uimIBv.rst
@@ -0,0 +1,10 @@
+Added return values to lib2to3.refactor functions.
+
+:func:`lib2to3.refactor.refactor_file` now returns a status:
+
+* True: The file was written to.
+* False: The file was not written to.
+* None: The file could not be read.
+
+:func:`lib2to3.refactor.refactor_dir` now returns a list of all written
+files.