diff --git a/stream_chat/async_chat/channel.py b/stream_chat/async_chat/channel.py
index a66fb7f..c8023ea 100644
--- a/stream_chat/async_chat/channel.py
+++ b/stream_chat/async_chat/channel.py
@@ -1,3 +1,4 @@
+import datetime
 import json
 from typing import Any, Dict, Iterable, List, Optional, Union
 
@@ -94,6 +95,10 @@ async def add_members(
         self, members: Iterable[Dict], message: Dict = None, **options: Any
     ) -> StreamResponse:
         payload = {"add_members": members, "message": message, **options}
+        if "hide_history_before" in payload and isinstance(
+            payload["hide_history_before"], datetime.datetime
+        ):
+            payload["hide_history_before"] = payload["hide_history_before"].isoformat()
         return await self.client.post(self.url, data=payload)
 
     async def assign_roles(
diff --git a/stream_chat/base/channel.py b/stream_chat/base/channel.py
index 8e300a5..d49a3f7 100644
--- a/stream_chat/base/channel.py
+++ b/stream_chat/base/channel.py
@@ -196,7 +196,7 @@ def add_members(
 
         :param members: member objects to add
         :param message: An optional to show
-        :param options: additional options such as hide_history
+        :param options: additional options such as hide_history or hide_history_before
         :return:
         """
         pass
diff --git a/stream_chat/channel.py b/stream_chat/channel.py
index 2373811..f5ce5c7 100644
--- a/stream_chat/channel.py
+++ b/stream_chat/channel.py
@@ -1,3 +1,4 @@
+import datetime
 import json
 from typing import Any, Dict, Iterable, List, Optional, Union
 
@@ -95,6 +96,10 @@ def add_members(
         **options: Any,
     ) -> StreamResponse:
         payload = {"add_members": members, "message": message, **options}
+        if "hide_history_before" in payload and isinstance(
+            payload["hide_history_before"], datetime.datetime
+        ):
+            payload["hide_history_before"] = payload["hide_history_before"].isoformat()
         return self.client.post(self.url, data=payload)
 
     def assign_roles(