diff --git a/docs/content/en/docs-dev/user-guide/managing-application/defining-app-configuration/ecs.md b/docs/content/en/docs-dev/user-guide/managing-application/defining-app-configuration/ecs.md
index 54fe3ad3d3..523d93837f 100644
--- a/docs/content/en/docs-dev/user-guide/managing-application/defining-app-configuration/ecs.md
+++ b/docs/content/en/docs-dev/user-guide/managing-application/defining-app-configuration/ecs.md
@@ -144,6 +144,11 @@ spec:
       - name: ECS_CANARY_CLEAN
 ```
 
+## NOTE
+
+- When you use an ELB for deployments, all listener rules that have the same target groups as configured in app.pipecd.yaml will be controlled.
+- For more information and diagrams, see [Issue#4733 [ECS] Modify ELB listener rules other than defaults without adding config](https://github.com/pipe-cd/pipecd/pull/4733).
+
 ## Reference
 
 See [Configuration Reference](../../../configuration-reference/#ecs-application) for the full configuration.