diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5b64495ab..b9afa137d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Documented all API methods ([#335](https://github.com/opensearch-project/opensearch-js/issues/335))
 - Added point in time APIs ([#348](https://github.com/opensearch-project/opensearch-js/pull/348))
 - Added support for Amazon OpenSearch Serverless ([#356](https://github.com/opensearch-project/opensearch-js/issues/356))
+- Added Amazon OpenSearch Serverless in user_guide ([#372](https://github.com/opensearch-project/opensearch-js/issues/372))
 
 ### Dependencies
 - Bumps `xmlbuilder2` from 2.4.1 to 3.0.2
diff --git a/USER_GUIDE.md b/USER_GUIDE.md
index 3ff5b7453..579c170e3 100644
--- a/USER_GUIDE.md
+++ b/USER_GUIDE.md
@@ -51,7 +51,8 @@ const { AwsSigv4Signer } = require('@opensearch-project/opensearch/aws');
 
 const client = new Client({
   ...AwsSigv4Signer({
-    region: 'us-east-1',
+    region: 'us-west-2',
+    service: 'es', // 'aoss' for OpenSearch Serverless
     // Must return a Promise that resolve to an AWS.Credentials object.
     // This function is used to acquire the credentials when the client start and
     // when the credentials are expired.
@@ -72,6 +73,7 @@ const client = new Client({
       }),
   }),
   node: 'https://search-xxx.region.es.amazonaws.com', // OpenSearch domain URL
+  // node: "https://xxx.region.aoss.amazonaws.com" for OpenSearch Serverless
 });
 ```
 
@@ -85,6 +87,7 @@ const { AwsSigv4Signer } = require('@opensearch-project/opensearch/aws');
 const client = new Client({
   ...AwsSigv4Signer({
     region: 'us-east-1',
+    service: 'es',  // 'aoss' for OpenSearch Serverless
     // Must return a Promise that resolve to an AWS.Credentials object.
     // This function is used to acquire the credentials when the client start and
     // when the credentials are expired.
@@ -99,6 +102,7 @@ const client = new Client({
     },
   }),
   node: 'https://search-xxx.region.es.amazonaws.com', // OpenSearch domain URL
+  // node: "https://xxx.region.aoss.amazonaws.com" for OpenSearch Serverless
 });
 ```