diff --git a/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-listener.ts b/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-listener.ts
index 4a4d66a952abb..cd3ca45ae2ce9 100644
--- a/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-listener.ts
+++ b/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-listener.ts
@@ -107,6 +107,11 @@ export class NetworkListener extends BaseListener implements INetworkListener {
    */
   private readonly loadBalancer: INetworkLoadBalancer;
 
+  /**
+   * the protocol of the listener
+   */
+  private readonly protocol: Protocol;
+
   constructor(scope: Construct, id: string, props: NetworkListenerProps) {
     const certs = props.certificates || [];
     const proto = props.protocol || (certs.length > 0 ? Protocol.TLS : Protocol.TCP);
@@ -130,6 +135,7 @@ export class NetworkListener extends BaseListener implements INetworkListener {
     });
 
     this.loadBalancer = props.loadBalancer;
+    this.protocol = proto;
 
     if (props.defaultAction && props.defaultTargetGroups) {
       throw new Error('Specify at most one of \'defaultAction\' and \'defaultTargetGroups\'');
@@ -189,6 +195,7 @@ export class NetworkListener extends BaseListener implements INetworkListener {
       deregistrationDelay: props.deregistrationDelay,
       healthCheck: props.healthCheck,
       port: props.port,
+      protocol: this.protocol,
       proxyProtocolV2: props.proxyProtocolV2,
       targetGroupName: props.targetGroupName,
       targets: props.targets,
diff --git a/packages/@aws-cdk/aws-elasticloadbalancingv2/test/nlb/test.listener.ts b/packages/@aws-cdk/aws-elasticloadbalancingv2/test/nlb/test.listener.ts
index 86a416e0a3ec9..9c16210a9ed68 100644
--- a/packages/@aws-cdk/aws-elasticloadbalancingv2/test/nlb/test.listener.ts
+++ b/packages/@aws-cdk/aws-elasticloadbalancingv2/test/nlb/test.listener.ts
@@ -86,6 +86,40 @@ export = {
     test.done();
   },
 
+  'implicitly created target group inherits protocol'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.Vpc(stack, 'Stack');
+    const lb = new elbv2.NetworkLoadBalancer(stack, 'LB', { vpc });
+    const listener = lb.addListener('Listener', { port: 9700, protocol: elbv2.Protocol.TCP_UDP });
+
+    // WHEN
+    listener.addTargets('Targets', {
+      port: 9700,
+      targets: [new elbv2.InstanceTarget('i-12345')],
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::ElasticLoadBalancingV2::Listener', {
+      DefaultActions: [
+        {
+          TargetGroupArn: { Ref: 'LBListenerTargetsGroup76EF81E8' },
+          Type: 'forward',
+        },
+      ],
+    }));
+    expect(stack).to(haveResource('AWS::ElasticLoadBalancingV2::TargetGroup', {
+      VpcId: { Ref: 'Stack8A423254' },
+      Port: 9700,
+      Protocol: 'TCP_UDP',
+      Targets: [
+        { Id: 'i-12345' },
+      ],
+    }));
+
+    test.done();
+  },
+
   'Enable health check for targets'(test: Test) {
     // GIVEN
     const stack = new cdk.Stack();