diff --git a/docarray/index/abstract.py b/docarray/index/abstract.py
index 17da44221d8..13f4837cd61 100644
--- a/docarray/index/abstract.py
+++ b/docarray/index/abstract.py
@@ -900,3 +900,6 @@ def _dict_list_to_docarray(self, dict_list: Sequence[Dict[str, Any]]) -> DocList
         doc_list = [self._convert_dict_to_doc(doc_dict, self._schema) for doc_dict in dict_list]  # type: ignore
         docs_cls = DocList.__class_getitem__(cast(Type[BaseDoc], self._schema))
         return docs_cls(doc_list)
+
+    def __len__(self) -> int:
+        return self.num_docs()
diff --git a/tests/index/base_classes/test_base_doc_store.py b/tests/index/base_classes/test_base_doc_store.py
index e3c8c455bba..83b5dcd45d2 100644
--- a/tests/index/base_classes/test_base_doc_store.py
+++ b/tests/index/base_classes/test_base_doc_store.py
@@ -71,7 +71,7 @@ def python_type_to_db_type(self, x):
         return str
 
     _index = _identity
-    num_docs = _identity
+    num_docs = lambda n: 3
     _del_items = _identity
     _get_items = _identity
     execute_query = _identity
@@ -572,3 +572,9 @@ def test_validate_search_fields():
     # 'ten' is not a valid field
     with pytest.raises(ValueError):
         index._validate_search_field('ten')
+
+
+def test_len():
+    store = DummyDocIndex[SimpleDoc]()
+    count = len(store)
+    assert count == 3