diff --git a/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/aws-ecs-integ-alb-idle-timeout.template.json b/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/aws-ecs-integ-alb-idle-timeout.template.json
index 909fc722fe04a..4ccc8a3069f81 100644
--- a/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/aws-ecs-integ-alb-idle-timeout.template.json
+++ b/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/aws-ecs-integ-alb-idle-timeout.template.json
@@ -906,7 +906,7 @@
      },
      {
       "Key": "idle_timeout.timeout_seconds",
-      "Value": "400"
+      "Value": "5"
      }
     ],
     "Scheme": "internet-facing",
@@ -1101,7 +1101,7 @@
      },
      {
       "Key": "idle_timeout.timeout_seconds",
-      "Value": "400"
+      "Value": "500"
      }
     ],
     "Scheme": "internet-facing",
diff --git a/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/tree.json b/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/tree.json
index e969dadbb6f31..4111a3f071c78 100644
--- a/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/tree.json
+++ b/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.js.snapshot/tree.json
@@ -1516,7 +1516,7 @@
                           },
                           {
                             "key": "idle_timeout.timeout_seconds",
-                            "value": "400"
+                            "value": "5"
                           }
                         ],
                         "scheme": "internet-facing",
@@ -1855,7 +1855,7 @@
                           },
                           {
                             "key": "idle_timeout.timeout_seconds",
-                            "value": "400"
+                            "value": "500"
                           }
                         ],
                         "scheme": "internet-facing",
diff --git a/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.ts b/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.ts
index 131e9c4999b38..fe8b376d154a3 100644
--- a/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.ts
+++ b/packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/ec2/integ.multiple-application-load-balanced-ecs-service-idle-timeout.ts
@@ -27,7 +27,7 @@ new ApplicationMultipleTargetGroupsEc2Service(stack, 'myService', {
   loadBalancers: [
     {
       name: 'lb',
-      idleTimeout: Duration.seconds(400),
+      idleTimeout: Duration.seconds(5),
       domainName: 'api.example.com',
       domainZone: zone,
       listeners: [
@@ -41,7 +41,7 @@ new ApplicationMultipleTargetGroupsEc2Service(stack, 'myService', {
     },
     {
       name: 'lb2',
-      idleTimeout: Duration.seconds(400),
+      idleTimeout: Duration.seconds(500),
       domainName: 'frontend.example.com',
       domainZone: zone,
       listeners: [
diff --git a/packages/aws-cdk-lib/aws-ecs-patterns/lib/base/application-multiple-target-groups-service-base.ts b/packages/aws-cdk-lib/aws-ecs-patterns/lib/base/application-multiple-target-groups-service-base.ts
index 7bdeeaa6fcd9a..9ac8750f6ff6c 100644
--- a/packages/aws-cdk-lib/aws-ecs-patterns/lib/base/application-multiple-target-groups-service-base.ts
+++ b/packages/aws-cdk-lib/aws-ecs-patterns/lib/base/application-multiple-target-groups-service-base.ts
@@ -306,7 +306,7 @@ export interface ApplicationLoadBalancerProps {
   readonly domainZone?: IHostedZone;
 
   /**
-   * The load balancer idle timeout, in seconds
+   * The load balancer idle timeout, in seconds. Can be between 1 and 4000 seconds.
    *
    * @default - CloudFormation sets idle timeout to 60 seconds
    */
@@ -585,7 +585,8 @@ export abstract class ApplicationMultipleTargetGroupsServiceBase extends Constru
   private validateLbProps(props: ApplicationLoadBalancerProps[]) {
     for (let prop of props) {
       if (prop.idleTimeout) {
-        if (prop.idleTimeout > Duration.seconds(4000) || prop.idleTimeout < Duration.seconds(1)) {
+        const idleTimeout = prop.idleTimeout.toSeconds();
+        if (idleTimeout > Duration.seconds(4000).toSeconds() || idleTimeout < Duration.seconds(1).toSeconds()) {
           throw new Error('Load balancer idle timeout must be between 1 and 4000 seconds.');
         }
       }
diff --git a/packages/aws-cdk-lib/aws-ecs-patterns/test/ec2/l3s.test.ts b/packages/aws-cdk-lib/aws-ecs-patterns/test/ec2/l3s.test.ts
index 74dd37aea2f5c..0c65e1ae77733 100644
--- a/packages/aws-cdk-lib/aws-ecs-patterns/test/ec2/l3s.test.ts
+++ b/packages/aws-cdk-lib/aws-ecs-patterns/test/ec2/l3s.test.ts
@@ -983,7 +983,7 @@ test('passes when idleTimeout is between 1 and 4000 seconds for multiAlbService'
       loadBalancers: [
         {
           name: 'lb',
-          idleTimeout: Duration.seconds(400),
+          idleTimeout: Duration.seconds(5),
           domainName: 'api.example.com',
           domainZone: new PublicHostedZone(stack, 'HostedZone', { zoneName: 'example.com' }),
           listeners: [
@@ -997,7 +997,7 @@ test('passes when idleTimeout is between 1 and 4000 seconds for multiAlbService'
         },
         {
           name: 'lb2',
-          idleTimeout: Duration.seconds(120),
+          idleTimeout: Duration.seconds(500),
           domainName: 'frontend.com',
           domainZone: new PublicHostedZone(stack, 'HostedZone2', { zoneName: 'frontend.com' }),
           listeners: [