diff --git a/ballerina/http_client_config.bal b/ballerina/http_client_config.bal
index c94f3b53b7..c427cd87bf 100644
--- a/ballerina/http_client_config.bal
+++ b/ballerina/http_client_config.bal
@@ -62,8 +62,10 @@ public type ResponseLimitConfigs record {|
 # Provides settings related to HTTP/2 protocol.
 #
 # + http2PriorKnowledge - Configuration to enable HTTP/2 prior knowledge
+# + http2InitialWindowSize - Configuration to change the initial window size
 public type ClientHttp2Settings record {|
     boolean http2PriorKnowledge = false;
+    int http2InitialWindowSize = 65535;
 |};
 
 # Provides configurations for controlling the retrying behavior in failure scenarios.
diff --git a/ballerina/http_service_endpoint.bal b/ballerina/http_service_endpoint.bal
index 7596b4b2ec..0dcff0b7b8 100644
--- a/ballerina/http_service_endpoint.bal
+++ b/ballerina/http_service_endpoint.bal
@@ -154,6 +154,7 @@ public type Local record {|
 # + interceptors - An array of interceptor services
 # + gracefulStopTimeout - Grace period of time in seconds for listener gracefulStop
 # + socketConfig - Provides settings related to server socket configuration
+# + http2InitialWindowSize - Configuration to change the initial window size in HTTP/2
 public type ListenerConfiguration record {|
     string host = "0.0.0.0";
     ListenerHttp1Settings http1Settings = {};
@@ -165,6 +166,7 @@ public type ListenerConfiguration record {|
     Interceptor|Interceptor[] interceptors?;
     decimal gracefulStopTimeout = DEFAULT_GRACEFULSTOP_TIMEOUT;
     ServerSocketConfig socketConfig = {};
+    int http2InitialWindowSize = 65535;
 |};
 
 # Provides a set of cloneable configurations for HTTP listener.
diff --git a/changelog.md b/changelog.md
index f140986535..843c7f800a 100644
--- a/changelog.md
+++ b/changelog.md
@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Add runtime support for type referenced type in path parameters](https://github.com/ballerina-platform/ballerina-standard-library/issues/4372)
 - [Add finite type support for query, header and path parameters](https://github.com/ballerina-platform/ballerina-standard-library/issues/4374)
 - [Support for service level interceptors using `http:InterceptableService`](https://github.com/ballerina-platform/ballerina-standard-library/issues/4401)
+- [Allow changing initial window size value for client and the server](https://github.com/ballerina-platform/ballerina-standard-library/issues/490)
 
 ### Changed
 
diff --git a/docs/spec/spec.md b/docs/spec/spec.md
index b88ee4ca68..ccbcfb4ef7 100644
--- a/docs/spec/spec.md
+++ b/docs/spec/spec.md
@@ -162,6 +162,7 @@ public type ListenerConfiguration record {|
     string? server = ();
     RequestLimitConfigs requestLimits = {};
     Interceptor|Interceptor[] interceptors?;
+    int http2InitialWindowSize = 65535;
 |};
 ```
 
@@ -1087,6 +1088,18 @@ public type ClientConfiguration record {|
     ProxyConfig? proxy = ();
     boolean validation = true;
 |};
+
+public type ClientHttp1Settings record {|
+    KeepAlive keepAlive = KEEPALIVE_AUTO;
+    Chunking chunking = CHUNKING_AUTO;
+    ProxyConfig? proxy = ();
+|};
+
+public type ClientHttp2Settings record {|
+    boolean http2PriorKnowledge = false;
+    int http2InitialWindowSize = 65535;
+|};
+
 ```
 
 Based on the config, the client object will be accompanied by following client behaviours. Following clients cannot be
diff --git a/native/spotbugs-exclude.xml b/native/spotbugs-exclude.xml
index 533d717970..1f870b31da 100644
--- a/native/spotbugs-exclude.xml
+++ b/native/spotbugs-exclude.xml
@@ -76,4 +76,8 @@
         <Class name="io.ballerina.stdlib.http.api.HttpService$1" />
         <Bug pattern="DM_EXIT" />
     </Match>
+    <Match>
+        <Class name="io.ballerina.stdlib.http.api.client.endpoint.CreateSimpleHttpClient" />
+        <Bug pattern="REC_CATCH_EXCEPTION" />
+    </Match>
 </FindBugsFilter>
diff --git a/native/src/main/java/io/ballerina/stdlib/http/api/HttpConstants.java b/native/src/main/java/io/ballerina/stdlib/http/api/HttpConstants.java
index f37cebc362..6a132b7d3f 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/api/HttpConstants.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/api/HttpConstants.java
@@ -415,6 +415,8 @@ public class HttpConstants {
     public static final BString ENDPOINT_CONFIG_VERSION = StringUtils.fromString("httpVersion");
     public static final String ENDPOINT_REQUEST_LIMITS = "requestLimits";
     public static final BString ENDPOINT_CONFIG_GRACEFUL_STOP_TIMEOUT = StringUtils.fromString("gracefulStopTimeout");
+    public static final BString ENDPOINT_CONFIG_HTTP2_INITIAL_WINDOW_SIZE = StringUtils
+            .fromString("http2InitialWindowSize");
 
     public static final BString MAX_URI_LENGTH = StringUtils.fromString("maxUriLength");
     public static final BString MAX_STATUS_LINE_LENGTH = StringUtils.fromString("maxStatusLineLength");
@@ -486,6 +488,8 @@ public class HttpConstants {
     public static final BString HTTP2_SETTINGS = StringUtils.fromString("http2Settings");
     public static final BString REQUEST_LIMITS = StringUtils.fromString("requestLimits");
     public static final BString RESPONSE_LIMITS = StringUtils.fromString("responseLimits");
+    public static final BString CLIENT_EP_HTTP2_INITIAL_WINDOW_SIZE = StringUtils
+            .fromString("http2InitialWindowSize");
 
     //Connection Throttling field names
     public static final String CONNECTION_THROTTLING_STRUCT_REFERENCE = "connectionThrottling";
diff --git a/native/src/main/java/io/ballerina/stdlib/http/api/HttpUtil.java b/native/src/main/java/io/ballerina/stdlib/http/api/HttpUtil.java
index 4277c277b6..aed668b5a5 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/api/HttpUtil.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/api/HttpUtil.java
@@ -130,6 +130,7 @@
 import static io.ballerina.runtime.observability.ObservabilityConstants.TAG_KEY_PEER_ADDRESS;
 import static io.ballerina.stdlib.http.api.HttpConstants.ANN_CONFIG_ATTR_COMPRESSION_CONTENT_TYPES;
 import static io.ballerina.stdlib.http.api.HttpConstants.ANN_CONFIG_ATTR_SSL_ENABLED_PROTOCOLS;
+import static io.ballerina.stdlib.http.api.HttpConstants.ENDPOINT_CONFIG_HTTP2_INITIAL_WINDOW_SIZE;
 import static io.ballerina.stdlib.http.api.HttpConstants.HTTP_HEADERS;
 import static io.ballerina.stdlib.http.api.HttpConstants.RESOLVED_REQUESTED_URI;
 import static io.ballerina.stdlib.http.api.HttpConstants.RESPONSE_CACHE_CONTROL;
@@ -1554,6 +1555,8 @@ public static ListenerConfiguration getListenerConfig(long port, BMap endpointCo
         }
 
         listenerConfiguration.setPipeliningEnabled(true); //Pipelining is enabled all the time
+        listenerConfiguration.setHttp2InitialWindowSize(endpointConfig
+                .getIntValue(ENDPOINT_CONFIG_HTTP2_INITIAL_WINDOW_SIZE).intValue());
         return listenerConfiguration;
     }
 
diff --git a/native/src/main/java/io/ballerina/stdlib/http/api/client/endpoint/CreateSimpleHttpClient.java b/native/src/main/java/io/ballerina/stdlib/http/api/client/endpoint/CreateSimpleHttpClient.java
index f65a9d72f3..a22b0ca0fd 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/api/client/endpoint/CreateSimpleHttpClient.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/api/client/endpoint/CreateSimpleHttpClient.java
@@ -35,6 +35,7 @@
 import java.net.URL;
 import java.util.Map;
 
+import static io.ballerina.stdlib.http.api.HttpConstants.CLIENT_EP_HTTP2_INITIAL_WINDOW_SIZE;
 import static io.ballerina.stdlib.http.api.HttpConstants.HTTP2_PRIOR_KNOWLEDGE;
 import static io.ballerina.stdlib.http.api.HttpConstants.SOCKET_CONFIG_CONNECT_TIMEOUT;
 import static io.ballerina.stdlib.http.api.HttpConstants.SOCKET_CONFIG_KEEP_ALIVE;
@@ -100,6 +101,8 @@ public static Object createSimpleHttpClient(BObject httpClient, BMap globalPoolC
                         get(HttpConstants.HTTP2_SETTINGS);
                 boolean http2PriorKnowledge = (boolean) http2Settings.get(HTTP2_PRIOR_KNOWLEDGE);
                 senderConfiguration.setForceHttp2(http2PriorKnowledge);
+                senderConfiguration.setHttp2InitialWindowSize(http2Settings
+                        .getIntValue(CLIENT_EP_HTTP2_INITIAL_WINDOW_SIZE).intValue());
             } else {
                 BMap<BString, Object> http1Settings = (BMap<BString, Object>) clientEndpointConfig.get(
                         HttpConstants.HTTP1_SETTINGS);
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/ListenerConfiguration.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/ListenerConfiguration.java
index 0c80f6db81..53d4c885df 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/ListenerConfiguration.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/ListenerConfiguration.java
@@ -63,6 +63,7 @@ public static ListenerConfiguration getDefault() {
     private boolean tcpNoDelay;
     private boolean socketReuse;
     private boolean socketKeepAlive;
+    private int http2InitialWindowSize = 65535;
 
     public ListenerConfiguration() {
     }
@@ -273,4 +274,12 @@ public boolean isSocketKeepAlive() {
     public void setSocketKeepAlive(boolean keepAlive) {
         this.socketKeepAlive = keepAlive;
     }
+
+    public int getHttp2InitialWindowSize() {
+        return http2InitialWindowSize;
+    }
+
+    public void setHttp2InitialWindowSize(int http2InitialWindowSize) {
+        this.http2InitialWindowSize = http2InitialWindowSize;
+    }
 }
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/SenderConfiguration.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/SenderConfiguration.java
index 2b89a99386..9c6b41022b 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/SenderConfiguration.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contract/config/SenderConfiguration.java
@@ -55,6 +55,7 @@ public static SenderConfiguration getDefault() {
     private boolean tcpNoDelay = true;
     private boolean socketReuse = false;
     private boolean socketKeepAlive = true;
+    private int http2InitialWindowSize = 65535;
 
     public SenderConfiguration() {
         this.poolConfiguration = new PoolConfiguration();
@@ -205,4 +206,12 @@ public boolean isSocketKeepAlive() {
     public void setSocketKeepAlive(boolean socketKeepAlive) {
         this.socketKeepAlive = socketKeepAlive;
     }
+
+    public int getHttp2InitialWindowSize() {
+        return http2InitialWindowSize;
+    }
+
+    public void setHttp2InitialWindowSize(int http2InitialWindowSize) {
+        this.http2InitialWindowSize = http2InitialWindowSize;
+    }
 }
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/DefaultHttpWsConnectorFactory.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/DefaultHttpWsConnectorFactory.java
index bca7825d7d..146e78ed62 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/DefaultHttpWsConnectorFactory.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/DefaultHttpWsConnectorFactory.java
@@ -90,6 +90,7 @@ public ServerConnector createServerConnector(ServerBootstrapConfiguration server
         serverConnectorBootstrap.addIdleTimeout(listenerConfig.getSocketIdleTimeout());
         if (Constants.HTTP_2_0.equals(listenerConfig.getVersion())) {
             serverConnectorBootstrap.setHttp2Enabled(true);
+            serverConnectorBootstrap.setHttp2InitialWindowSize(listenerConfig.getHttp2InitialWindowSize());
         }
         serverConnectorBootstrap.addHttpTraceLogHandler(listenerConfig.isHttpTraceLogEnabled());
         serverConnectorBootstrap.addHttpAccessLogHandler(listenerConfig.isHttpAccessLogEnabled());
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/HttpServerChannelInitializer.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/HttpServerChannelInitializer.java
index 233f238305..184731c93b 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/HttpServerChannelInitializer.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/HttpServerChannelInitializer.java
@@ -108,6 +108,7 @@ public class HttpServerChannelInitializer extends ChannelInitializer<SocketChann
     private long pipeliningLimit;
     private EventExecutorGroup pipeliningGroup;
     private boolean webSocketCompressionEnabled;
+    private int http2InitialWindowSize;
 
     @Override
     public void initChannel(SocketChannel ch) throws Exception {
@@ -254,7 +255,7 @@ private void configureH2cPipeline(ChannelPipeline pipeline) {
         // Add handler to handle http2 requests without an upgrade
         pipeline.addLast(new Http2WithPriorKnowledgeHandler(
                 interfaceId, serverName, serverConnectorFuture, this, allChannels, listenerChannels,
-                reqSizeValidationConfig.getMaxHeaderSize()));
+                reqSizeValidationConfig.getMaxHeaderSize(), http2InitialWindowSize));
         // Add http2 upgrade decoder and upgrade handler
         final HttpServerCodec sourceCodec = new HttpServerCodec(reqSizeValidationConfig.getMaxInitialLineLength(),
                                                                 reqSizeValidationConfig.getMaxHeaderSize(),
@@ -276,8 +277,8 @@ private void configureH2cPipeline(ChannelPipeline pipeline) {
                         Constants.HTTP2_SOURCE_CONNECTION_HANDLER,
                         new Http2SourceConnectionHandlerBuilder(
                                 interfaceId, serverConnectorFuture, serverName, this,
-                                this.allChannels, this.listenerChannels,
-                                reqSizeValidationConfig.getMaxHeaderSize()).build());
+                                this.allChannels, this.listenerChannels, reqSizeValidationConfig.getMaxHeaderSize(),
+                                this.http2InitialWindowSize).build());
             } else {
                 return null;
             }
@@ -347,6 +348,10 @@ void setReqSizeValidationConfig(InboundMsgSizeValidationConfig reqSizeValidation
         this.reqSizeValidationConfig = reqSizeValidationConfig;
     }
 
+    void setHttp2InitialWindowSize(int http2InitialWindowSize) {
+        this.http2InitialWindowSize = http2InitialWindowSize;
+    }
+
     public void setChunkingConfig(ChunkConfig chunkConfig) {
         this.chunkConfig = chunkConfig;
     }
@@ -426,7 +431,8 @@ protected void configurePipeline(ChannelHandlerContext ctx, String protocol) {
                         Constants.HTTP2_SOURCE_CONNECTION_HANDLER,
                         new Http2SourceConnectionHandlerBuilder(
                                 interfaceId, serverConnectorFuture, serverName, channelInitializer,
-                                allChannels, listenerChannels, reqSizeValidationConfig.getMaxHeaderSize()).build());
+                                allChannels, listenerChannels, reqSizeValidationConfig.getMaxHeaderSize(),
+                                http2InitialWindowSize).build());
             } else if (ApplicationProtocolNames.HTTP_1_1.equals(protocol)) {
                 // handles pipeline for HTTP/1.x requests after SSL handshake
                 configureHttpPipeline(ctx.pipeline(), Constants.HTTP_SCHEME);
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/ServerConnectorBootstrap.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/ServerConnectorBootstrap.java
index f70ceff88c..85d84bb9f2 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/ServerConnectorBootstrap.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/ServerConnectorBootstrap.java
@@ -197,6 +197,10 @@ public void setWebSocketCompressionEnabled(boolean webSocketCompressionEnabled)
         httpServerChannelInitializer.setWebSocketCompressionEnabled(webSocketCompressionEnabled);
     }
 
+    public void setHttp2InitialWindowSize(int http2InitialWindowSize) {
+        httpServerChannelInitializer.setHttp2InitialWindowSize(http2InitialWindowSize);
+    }
+
     public ChannelGroup getListenerChannels() {
         return listenerChannels;
     }
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2SourceConnectionHandlerBuilder.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2SourceConnectionHandlerBuilder.java
index 925e9b1bd9..bb6117f7fc 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2SourceConnectionHandlerBuilder.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2SourceConnectionHandlerBuilder.java
@@ -53,7 +53,8 @@ public Http2SourceConnectionHandlerBuilder(String interfaceId, ServerConnectorFu
                                                HttpServerChannelInitializer serverChannelInitializer,
                                                ChannelGroup allChannels,
                                                ChannelGroup listenerChannels,
-                                               long maxHeaderListSize) {
+                                               long maxHeaderListSize,
+                                               int initialWindowSize) {
         this.interfaceId = interfaceId;
         this.serverConnectorFuture = serverConnectorFuture;
         this.serverName = serverName;
@@ -61,6 +62,7 @@ public Http2SourceConnectionHandlerBuilder(String interfaceId, ServerConnectorFu
         this.allChannels = allChannels;
         this.listenerChannels = listenerChannels;
         this.initialSettings().maxHeaderListSize(maxHeaderListSize);
+        this.initialSettings().initialWindowSize(initialWindowSize);
     }
 
     @Override
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2WithPriorKnowledgeHandler.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2WithPriorKnowledgeHandler.java
index 3b73d63420..897a75f4e5 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2WithPriorKnowledgeHandler.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/listener/http2/Http2WithPriorKnowledgeHandler.java
@@ -48,13 +48,15 @@ public class Http2WithPriorKnowledgeHandler extends ChannelInboundHandlerAdapter
     private ChannelGroup allChannels;
     private ChannelGroup listenerChannels;
     private long maxHeaderListSize;
+    private int initialWindowSize;
 
     public Http2WithPriorKnowledgeHandler(String interfaceId, String serverName,
                                           ServerConnectorFuture serverConnectorFuture,
                                           HttpServerChannelInitializer serverChannelInitializer,
                                           ChannelGroup allChannels,
                                           ChannelGroup listenerChannels,
-                                          long maxHeaderListSize) {
+                                          long maxHeaderListSize,
+                                          int initialWindowSize) {
         this.interfaceId = interfaceId;
         this.serverName = serverName;
         this.serverConnectorFuture = serverConnectorFuture;
@@ -62,6 +64,7 @@ public Http2WithPriorKnowledgeHandler(String interfaceId, String serverName,
         this.allChannels = allChannels;
         this.listenerChannels = listenerChannels;
         this.maxHeaderListSize = maxHeaderListSize;
+        this.initialWindowSize = initialWindowSize;
     }
 
     @Override
@@ -80,8 +83,7 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) {
                         Constants.HTTP2_SOURCE_CONNECTION_HANDLER,
                         new Http2SourceConnectionHandlerBuilder(
                                 interfaceId, serverConnectorFuture, serverName, serverChannelInitializer,
-                                allChannels, listenerChannels, maxHeaderListSize).build());
-
+                                allChannels, listenerChannels, maxHeaderListSize, initialWindowSize).build());
                 safelyRemoveHandlers(pipeline, Constants.HTTP2_UPGRADE_HANDLER,
                         Constants.HTTP_COMPRESSOR, Constants.HTTP_TRACE_LOG_HANDLER);
             }
diff --git a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/sender/HttpClientChannelInitializer.java b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/sender/HttpClientChannelInitializer.java
index f72c11ca8d..8b83a42147 100644
--- a/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/sender/HttpClientChannelInitializer.java
+++ b/native/src/main/java/io/ballerina/stdlib/http/transport/contractimpl/sender/HttpClientChannelInitializer.java
@@ -117,6 +117,7 @@ public HttpClientChannelInitializer(SenderConfiguration senderConfiguration, Htt
         if (httpTraceLogEnabled) {
             connectionHandlerBuilder.frameLogger(new FrameLogger(TRACE, Constants.TRACE_LOG_UPSTREAM));
         }
+        connectionHandlerBuilder.initialSettings().initialWindowSize(senderConfiguration.getHttp2InitialWindowSize());
         http2ConnectionHandler = connectionHandlerBuilder.connection(connection).frameListener(frameListener).build();
         http2TargetHandler = new Http2TargetHandler(connection, http2ConnectionHandler.encoder());
         if (sslConfig != null) {