diff --git a/backend/chainlit/teams/app.py b/backend/chainlit/teams/app.py
index 6d420ef85e..1de0acbea8 100644
--- a/backend/chainlit/teams/app.py
+++ b/backend/chainlit/teams/app.py
@@ -129,6 +129,7 @@ async def update_step(self, step_dict: StepDict):
 adapter_settings = BotFrameworkAdapterSettings(
     app_id=os.environ.get("TEAMS_APP_ID"),
     app_password=os.environ.get("TEAMS_APP_PASSWORD"),
+    channel_auth_tenant=os.environ.get("TEAMS_APP_TENANT_ID"),
 )
 adapter = BotFrameworkAdapter(adapter_settings)
 
diff --git a/backend/tests/test_teams_adapter.py b/backend/tests/test_teams_adapter.py
new file mode 100644
index 0000000000..64e4ac92e4
--- /dev/null
+++ b/backend/tests/test_teams_adapter.py
@@ -0,0 +1,58 @@
+import importlib
+from unittest.mock import MagicMock, call, patch
+
+
+def _reload_teams_app(monkeypatch, env_vars: dict):
+    """Reload chainlit.teams.app with the given environment variables set."""
+    for key, value in env_vars.items():
+        monkeypatch.setenv(key, value)
+    # Remove keys not in env_vars so tests are independent
+    for key in ("TEAMS_APP_ID", "TEAMS_APP_PASSWORD", "TEAMS_APP_TENANT_ID"):
+        if key not in env_vars:
+            monkeypatch.delenv(key, raising=False)
+
+    teams_mod = importlib.import_module("chainlit.teams.app")
+    return importlib.reload(teams_mod)
+
+
+def test_teams_adapter_without_tenant(monkeypatch):
+    """Omitting TEAMS_APP_TENANT_ID leaves channel_auth_tenant as None (multi-tenant)."""
+    with (
+        patch("botbuilder.core.BotFrameworkAdapterSettings") as mock_settings,
+        patch("botbuilder.core.BotFrameworkAdapter"),
+    ):
+        mock_settings.return_value = MagicMock()
+        _reload_teams_app(
+            monkeypatch,
+            {"TEAMS_APP_ID": "app-id", "TEAMS_APP_PASSWORD": "app-secret"},
+        )
+        assert mock_settings.call_count >= 1
+        assert mock_settings.call_args_list[-1] == call(
+            app_id="app-id",
+            app_password="app-secret",
+            channel_auth_tenant=None,
+        )
+
+
+def test_teams_adapter_with_tenant(monkeypatch):
+    """Setting TEAMS_APP_TENANT_ID forwards the tenant to BotFrameworkAdapterSettings."""
+    tenant_id = "00000000-0000-0000-0000-000000000001"
+    with (
+        patch("botbuilder.core.BotFrameworkAdapterSettings") as mock_settings,
+        patch("botbuilder.core.BotFrameworkAdapter"),
+    ):
+        mock_settings.return_value = MagicMock()
+        _reload_teams_app(
+            monkeypatch,
+            {
+                "TEAMS_APP_ID": "app-id",
+                "TEAMS_APP_PASSWORD": "app-secret",
+                "TEAMS_APP_TENANT_ID": tenant_id,
+            },
+        )
+        assert mock_settings.call_count >= 1
+        assert mock_settings.call_args_list[-1] == call(
+            app_id="app-id",
+            app_password="app-secret",
+            channel_auth_tenant=tenant_id,
+        )