diff --git a/langchain/chains/combine_documents/map_reduce.py b/langchain/chains/combine_documents/map_reduce.py
index 06e87e03..84e49296 100644
--- a/langchain/chains/combine_documents/map_reduce.py
+++ b/langchain/chains/combine_documents/map_reduce.py
@@ -163,16 +163,18 @@ class MapReduceDocumentsChain(BaseCombineDocumentsChain):
             [{**{self.document_variable_name: d.page_content}, **kwargs} for d in docs],
             callbacks=callbacks,
         )
-        return self._process_results(results, docs, callbacks=callbacks, **kwargs)
+        return await self._aprocess_results(
+            results, docs, callbacks=callbacks, **kwargs
+        )
 
-    def _process_results(
+    def _process_results_common(
         self,
         results: List[Dict],
         docs: List[Document],
         token_max: int = 3000,
         callbacks: Callbacks = None,
         **kwargs: Any,
-    ) -> Tuple[str, dict]:
+    ) -> Tuple[List[Document], dict]:
         question_result_key = self.llm_chain.output_key
         result_docs = [
             Document(page_content=r[question_result_key], metadata=docs[i].metadata)
@@ -201,11 +203,39 @@ class MapReduceDocumentsChain(BaseCombineDocumentsChain):
             extra_return_dict = {"intermediate_steps": _results}
         else:
             extra_return_dict = {}
+        return result_docs, extra_return_dict
+
+    def _process_results(
+        self,
+        results: List[Dict],
+        docs: List[Document],
+        token_max: int = 3000,
+        callbacks: Callbacks = None,
+        **kwargs: Any,
+    ) -> Tuple[str, dict]:
+        result_docs, extra_return_dict = self._process_results_common(
+            results, docs, token_max, callbacks=callbacks, **kwargs
+        )
         output = self.combine_document_chain.run(
             input_documents=result_docs, callbacks=callbacks, **kwargs
         )
         return output, extra_return_dict
 
+    async def _aprocess_results(
+        self,
+        results: List[Dict],
+        docs: List[Document],
+        callbacks: Callbacks = None,
+        **kwargs: Any,
+    ) -> Tuple[str, dict]:
+        result_docs, extra_return_dict = self._process_results_common(
+            results, docs, callbacks=callbacks, **kwargs
+        )
+        output = await self.combine_document_chain.arun(
+            input_documents=result_docs, callbacks=callbacks, **kwargs
+        )
+        return output, extra_return_dict
+
     @property
     def _chain_type(self) -> str:
         return "map_reduce_documents_chain"