diff --git a/CHANGELOG.md b/CHANGELOG.md
index 31ac61e..d90c157 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 - `CanonicalizedMap`: added constructor `fromEntries`.
 - Require Dart `^3.1.0`
 - Mark "mixin" classes as `mixin`.
+- Deprecate `transitiveClosure`. Consider using `package:graphs`.
 
 ## 1.18.0
 
diff --git a/lib/src/functions.dart b/lib/src/functions.dart
index 8f60b26..fb67c9f 100644
--- a/lib/src/functions.dart
+++ b/lib/src/functions.dart
@@ -120,6 +120,7 @@ S? maxBy<S, T>(Iterable<S> values, T Function(S) orderBy,
 /// that vertex has no outgoing edges. This isn't checked, but if it's not
 /// satisfied, the function may crash or provide unexpected output. For example,
 /// `{"a": ["b"]}` is not valid, but `{"a": ["b"], "b": []}` is.
+@Deprecated('This method will be removed. Consider using package:graphs.')
 Map<T, Set<T>> transitiveClosure<T>(Map<T, Iterable<T>> graph) {
   // This uses [Warshall's algorithm][], modified not to add a vertex from each
   // node to itself.
diff --git a/test/functions_test.dart b/test/functions_test.dart
index cc97327..f602303 100644
--- a/test/functions_test.dart
+++ b/test/functions_test.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// ignore_for_file: deprecated_member_use_from_same_package
+
 import 'package:collection/collection.dart';
 import 'package:test/test.dart';
 
@@ -9,7 +11,6 @@ void main() {
   group('mapMap()', () {
     test('with an empty map returns an empty map', () {
       expect(
-          // ignore: deprecated_member_use_from_same_package
           mapMap({},
               key: expectAsync2((_, __) {}, count: 0),
               value: expectAsync2((_, __) {}, count: 0)),
@@ -18,7 +19,6 @@ void main() {
 
     test('with no callbacks, returns a copy of the map', () {
       var map = {'foo': 1, 'bar': 2};
-      // ignore: deprecated_member_use_from_same_package
       var result = mapMap<String, int, String, int>(map);
       expect(result, equals({'foo': 1, 'bar': 2}));
 
@@ -29,7 +29,6 @@ void main() {
 
     test("maps the map's keys", () {
       expect(
-          // ignore: deprecated_member_use_from_same_package
           mapMap<String, int, dynamic, int>({'foo': 1, 'bar': 2},
               key: (dynamic key, dynamic value) => key[value]),
           equals({'o': 1, 'r': 2}));
@@ -37,7 +36,6 @@ void main() {
 
     test("maps the map's values", () {
       expect(
-          // ignore: deprecated_member_use_from_same_package
           mapMap<String, int, String, dynamic>({'foo': 1, 'bar': 2},
               value: (dynamic key, dynamic value) => key[value]),
           equals({'foo': 'o', 'bar': 'r'}));
@@ -45,7 +43,6 @@ void main() {
 
     test("maps both the map's keys and values", () {
       expect(
-          // ignore: deprecated_member_use_from_same_package
           mapMap({'foo': 1, 'bar': 2},
               key: (dynamic key, dynamic value) => '$key$value',
               value: (dynamic key, dynamic value) => key[value]),