diff --git a/mmengine/hooks/checkpoint_hook.py b/mmengine/hooks/checkpoint_hook.py
index 92a4867bb9..62194cf138 100644
--- a/mmengine/hooks/checkpoint_hook.py
+++ b/mmengine/hooks/checkpoint_hook.py
@@ -326,6 +326,11 @@ def before_train(self, runner) -> None:
             self.keep_ckpt_ids: deque = deque(keep_ckpt_ids,
                                               self.max_keep_ckpts)
 
+    def before_val(self, runner) -> None:
+        """Initialize checkpoint state when validation runs standalone."""
+        if not hasattr(self, 'file_backend'):
+            self.before_train(runner)
+
     def after_train_epoch(self, runner) -> None:
         """Save the checkpoint and synchronize buffers after each epoch.
 
diff --git a/tests/test_hooks/test_checkpoint_hook.py b/tests/test_hooks/test_checkpoint_hook.py
index 13914341f7..dc02a76e81 100644
--- a/tests/test_hooks/test_checkpoint_hook.py
+++ b/tests/test_hooks/test_checkpoint_hook.py
@@ -336,7 +336,6 @@ def test_after_val_epoch(self):
         petrel_client = MagicMock()
         for by_epoch, cfg in [(True, self.epoch_based_cfg),
                               (False, self.iter_based_cfg)]:
-            isfile = MagicMock(return_value=True)
             self.clear_work_dir()
             with patch.dict(sys.modules, {'petrel_client': petrel_client}), \
                  patch('mmengine.fileio.backends.PetrelBackend.put') as put_mock, \
@@ -362,6 +361,17 @@ def test_after_val_epoch(self):
                 isfile.assert_called_once()
                 remove_mock.assert_called_once()
 
+    def test_before_val_initializes_save_best(self):
+        runner = self.build_runner(self.epoch_based_cfg)
+        checkpoint_hook = CheckpointHook(save_best='acc')
+
+        checkpoint_hook.before_val(runner)
+        checkpoint_hook.after_val_epoch(runner, {'acc': 0.5})
+
+        self.assertEqual(runner.message_hub.get_info('best_score'), 0.5)
+        self.assertTrue(
+            osp.isfile(osp.join(runner.work_dir, 'best_acc_epoch_0.pth')))
+
     def test_after_train_epoch(self):
         cfg = copy.deepcopy(self.epoch_based_cfg)
         runner = self.build_runner(cfg)