diff --git a/litellm/integrations/SlackAlerting/slack_alerting.py b/litellm/integrations/SlackAlerting/slack_alerting.py
index 7da38e193b69..3efe58737865 100644
--- a/litellm/integrations/SlackAlerting/slack_alerting.py
+++ b/litellm/integrations/SlackAlerting/slack_alerting.py
@@ -134,6 +134,27 @@ def update_values(
         if llm_router is not None:
             self.llm_router = llm_router
 
+    def _prepare_outage_value_for_cache(self, outage_value: Union[dict, ProviderRegionOutageModel, OutageModel]) -> dict:
+        """
+        Helper method to prepare outage value for Redis caching.
+        Converts set objects to lists for JSON serialization.
+        """
+        # Convert to dict for processing
+        cache_value = dict(outage_value)
+        
+        if "deployment_ids" in cache_value and isinstance(cache_value["deployment_ids"], set):
+            cache_value["deployment_ids"] = list(cache_value["deployment_ids"])
+        return cache_value
+
+    def _restore_outage_value_from_cache(self, outage_value: Optional[dict]) -> Optional[dict]:
+        """
+        Helper method to restore outage value after retrieving from cache.
+        Converts list objects back to sets for proper handling.
+        """
+        if outage_value and isinstance(outage_value.get("deployment_ids"), list):
+            outage_value["deployment_ids"] = set(outage_value["deployment_ids"])
+        return outage_value
+
     async def deployment_in_cooldown(self):
         pass
 
@@ -809,6 +830,10 @@ async def region_outage_alerts(
             ProviderRegionOutageModel
         ] = await self.internal_usage_cache.async_get_cache(key=cache_key)
 
+        # Convert deployment_ids back to set if it was stored as a list
+        if outage_value is not None:
+            outage_value = self._restore_outage_value_from_cache(outage_value)  # type: ignore
+
         if (
             getattr(exception, "status_code", None) is None
             or (
@@ -832,9 +857,11 @@ async def region_outage_alerts(
             )
 
             ## add to cache ##
+            # Convert set to list for JSON serialization
+            cache_value = self._prepare_outage_value_for_cache(outage_value)
             await self.internal_usage_cache.async_set_cache(
                 key=cache_key,
-                value=outage_value,
+                value=cache_value,
                 ttl=self.alerting_args.region_outage_alert_ttl,
             )
             return
@@ -900,8 +927,10 @@ async def region_outage_alerts(
             outage_value["major_alert_sent"] = True
 
         ## update cache ##
+        # Convert set to list for JSON serialization
+        cache_value = self._prepare_outage_value_for_cache(outage_value)
         await self.internal_usage_cache.async_set_cache(
-            key=cache_key, value=outage_value
+            key=cache_key, value=cache_value
         )
 
     async def outage_alerts(
@@ -1025,8 +1054,10 @@ async def outage_alerts(
                 outage_value["major_alert_sent"] = True
 
             ## update cache ##
+            # Convert set to list for JSON serialization
+            cache_value = self._prepare_outage_value_for_cache(outage_value)
             await self.internal_usage_cache.async_set_cache(
-                key=deployment_id, value=outage_value
+                key=deployment_id, value=cache_value
             )
         except Exception:
             pass
diff --git a/tests/test_litellm/integrations/SlackAlerting/test_slack_alerting.py b/tests/test_litellm/integrations/SlackAlerting/test_slack_alerting.py
index 9cccdb517995..128a88a0f129 100644
--- a/tests/test_litellm/integrations/SlackAlerting/test_slack_alerting.py
+++ b/tests/test_litellm/integrations/SlackAlerting/test_slack_alerting.py
@@ -196,3 +196,47 @@ def test_alert_type_in_formatted_message(self, mock_datetime):
         self.assertIn("Level: `Medium`", formatted_message)
         self.assertIn("Timestamp: `12:34:56`", formatted_message)
         self.assertIn("Message: Test alert message", formatted_message)
+
+    def test_original_redis_error_reproduction(self):
+        """Test that reproduces the original Redis serialization error."""
+        # This test verifies that the original error would occur without our fix
+        outage_value = {
+            "alerts": [408],
+            "deployment_ids": {"zapier-multi-provider-gemini-2.5-flash-1ite-vertex"},
+            "last_updated_at": 1760601633.6620142,
+            "major_alert_sent": False,
+            "minor_alert_sent": False,
+            "provider_region_id": "vertex_aius-east1"
+        }
+        
+        # This should raise a TypeError due to set not being JSON serializable
+        with self.assertRaises(TypeError) as context:
+            json.dumps(outage_value)
+        
+        # Verify the specific error message
+        self.assertIn("Object of type set is not JSON serializable", str(context.exception))
+
+    def test_fixed_redis_serialization(self):
+        """Test that our fix resolves the Redis serialization error."""
+        # Same data that caused the original error
+        outage_value = {
+            "alerts": [408],
+            "deployment_ids": {"zapier-multi-provider-gemini-2.5-flash-1ite-vertex"},
+            "last_updated_at": 1760601633.6620142,
+            "major_alert_sent": False,
+            "minor_alert_sent": False,
+            "provider_region_id": "vertex_aius-east1"
+        }
+        
+        # Apply our fix
+        cache_value = self.slack_alerting._prepare_outage_value_for_cache(outage_value)
+        
+        # This should now work without errors
+        json_str = json.dumps(cache_value)
+        self.assertIsInstance(json_str, str)
+        
+        # Verify the data is correct
+        parsed_data = json.loads(json_str)
+        self.assertEqual(parsed_data["deployment_ids"], ["zapier-multi-provider-gemini-2.5-flash-1ite-vertex"])
+        self.assertEqual(parsed_data["alerts"], [408])
+        self.assertEqual(parsed_data["provider_region_id"], "vertex_aius-east1")