diff --git a/CHANGELOG.md b/CHANGELOG.md
index f3bf18332..024b8332a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 Lists all changes with user impact.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
+## [0.20.4]
+
+### Changed
+- Added possibility to add response header for weighted secondary cluster 
 
 ## [0.20.3]
 
diff --git a/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/SnapshotProperties.kt b/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/SnapshotProperties.kt
index 9590a1801..196b4b6cf 100644
--- a/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/SnapshotProperties.kt
+++ b/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/SnapshotProperties.kt
@@ -157,6 +157,7 @@ class CanaryProperties {
 
 class TrafficSplittingProperties {
     var zoneName = ""
+    var headerName = ""
     var serviceByWeightsProperties: Map<String, ZoneWeights> = mapOf()
     var secondaryClusterSuffix = "secondary"
     var aggregateClusterSuffix = "aggregate"
diff --git a/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactory.kt b/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactory.kt
index bb09953f2..021444709 100644
--- a/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactory.kt
+++ b/envoy-control-core/src/main/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactory.kt
@@ -36,6 +36,7 @@ import pl.allegro.tech.servicemesh.envoycontrol.snapshot.StandardRouteSpecificat
 import pl.allegro.tech.servicemesh.envoycontrol.snapshot.WeightRouteSpecification
 import pl.allegro.tech.servicemesh.envoycontrol.snapshot.resource.clusters.EnvoyClustersFactory.Companion.getAggregateClusterName
 import pl.allegro.tech.servicemesh.envoycontrol.snapshot.resource.listeners.filters.ServiceTagFilterFactory
+import java.lang.Boolean.TRUE
 import pl.allegro.tech.servicemesh.envoycontrol.groups.RetryPolicy as EnvoyControlRetryPolicy
 
 class EnvoyEgressRoutesFactory(
@@ -359,7 +360,8 @@ class EnvoyEgressRoutesFactory(
                         .withClusterWeight(routeSpec.clusterName, routeSpec.clusterWeights.main)
                         .withClusterWeight(
                             getAggregateClusterName(routeSpec.clusterName, properties),
-                            routeSpec.clusterWeights.secondary
+                            routeSpec.clusterWeights.secondary,
+                            true
                         )
                 )
             }
@@ -369,15 +371,40 @@ class EnvoyEgressRoutesFactory(
         }
     }
 
-    private fun WeightedCluster.Builder.withClusterWeight(clusterName: String, weight: Int): WeightedCluster.Builder {
-        this.addClusters(
-            WeightedCluster.ClusterWeight.newBuilder()
-                .setName(clusterName)
-                .setWeight(UInt32Value.of(weight))
-                .build()
-        )
+    private fun WeightedCluster.Builder.withClusterWeight(
+        clusterName: String,
+        weight: Int,
+        withHeader: Boolean = false
+    ): WeightedCluster.Builder {
+        val clusters = WeightedCluster.ClusterWeight.newBuilder()
+            .setName(clusterName)
+            .setWeight(UInt32Value.of(weight))
+            .also {
+                if (withHeader) {
+                    it.withHeader(properties.loadBalancing.trafficSplitting.headerName)
+                }
+            }
+        return this.addClusters(clusters)
+    }
+
+    private fun WeightedCluster.ClusterWeight.Builder.withHeader(key: String?): WeightedCluster.ClusterWeight.Builder {
+        key?.takeIf { it.isNotBlank() }
+            ?.let {
+                this.addResponseHeadersToAdd(buildHeader(key))
+            }
         return this
     }
+
+    private fun buildHeader(key: String): HeaderValueOption.Builder {
+        return HeaderValueOption.newBuilder()
+            .setHeader(
+                HeaderValue.newBuilder()
+                    .setKey(key)
+                    .setValue(TRUE.toString())
+            )
+            .setAppendAction(HeaderValueOption.HeaderAppendAction.OVERWRITE_IF_EXISTS_OR_ADD)
+            .setKeepEmptyValue(false)
+    }
 }
 
 class RequestPolicyMapper private constructor() {
diff --git a/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/groups/RoutesAssertions.kt b/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/groups/RoutesAssertions.kt
index d1162561c..ad89091ee 100644
--- a/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/groups/RoutesAssertions.kt
+++ b/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/groups/RoutesAssertions.kt
@@ -12,6 +12,7 @@ import io.envoyproxy.envoy.config.route.v3.RouteAction
 import io.envoyproxy.envoy.config.route.v3.RouteConfiguration
 import io.envoyproxy.envoy.config.route.v3.VirtualCluster
 import io.envoyproxy.envoy.config.route.v3.VirtualHost
+import io.envoyproxy.envoy.config.route.v3.WeightedCluster
 import io.envoyproxy.envoy.type.matcher.v3.RegexMatcher
 import org.assertj.core.api.Assertions.assertThat
 import pl.allegro.tech.servicemesh.envoycontrol.snapshot.LocalRetryPolicyProperties
@@ -27,6 +28,16 @@ fun RouteConfiguration.hasVirtualHostThat(name: String, condition: VirtualHost.(
     return this
 }
 
+fun RouteConfiguration.hasClusterThat(name: String, condition: WeightedCluster.ClusterWeight?.() -> Unit): RouteConfiguration {
+    condition(this.virtualHostsList
+        .flatMap { it.routesList }
+        .map { it.route }
+        .flatMap { route -> route.weightedClusters.clustersList }
+        .find { it.name == name }
+    )
+    return this
+}
+
 fun RouteConfiguration.hasRequestHeaderToAdd(key: String, value: String): RouteConfiguration {
     assertThat(this.requestHeadersToAddList).anySatisfy {
         assertThat(it.header.key).isEqualTo(key)
diff --git a/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactoryTest.kt b/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactoryTest.kt
index 93239bde0..2044699df 100644
--- a/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactoryTest.kt
+++ b/envoy-control-core/src/test/kotlin/pl/allegro/tech/servicemesh/envoycontrol/snapshot/resource/routes/EnvoyEgressRoutesFactoryTest.kt
@@ -2,10 +2,13 @@ package pl.allegro.tech.servicemesh.envoycontrol.snapshot.resource.routes
 
 import com.google.protobuf.util.Durations
 import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNotNull
+import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
 import pl.allegro.tech.servicemesh.envoycontrol.groups.DependencySettings
 import pl.allegro.tech.servicemesh.envoycontrol.groups.Outgoing
 import pl.allegro.tech.servicemesh.envoycontrol.groups.RetryPolicy
+import pl.allegro.tech.servicemesh.envoycontrol.groups.hasClusterThat
 import pl.allegro.tech.servicemesh.envoycontrol.groups.hasCustomIdleTimeout
 import pl.allegro.tech.servicemesh.envoycontrol.groups.hasCustomRequestTimeout
 import pl.allegro.tech.servicemesh.envoycontrol.groups.hasHostRewriteHeader
@@ -23,6 +26,8 @@ import pl.allegro.tech.servicemesh.envoycontrol.groups.matchingOnMethod
 import pl.allegro.tech.servicemesh.envoycontrol.groups.matchingOnPrefix
 import pl.allegro.tech.servicemesh.envoycontrol.snapshot.SnapshotProperties
 import pl.allegro.tech.servicemesh.envoycontrol.snapshot.StandardRouteSpecification
+import pl.allegro.tech.servicemesh.envoycontrol.snapshot.WeightRouteSpecification
+import pl.allegro.tech.servicemesh.envoycontrol.snapshot.ZoneWeights
 
 internal class EnvoyEgressRoutesFactoryTest {
 
@@ -42,6 +47,15 @@ internal class EnvoyEgressRoutesFactoryTest {
         )
     )
 
+    val weightedClusters = listOf(
+        WeightRouteSpecification(
+            clusterName = "srv1",
+            routeDomains = listOf("srv1"),
+            settings = DependencySettings(),
+            ZoneWeights()
+        )
+    )
+
     @Test
     fun `should add client identity header if incoming permissions are enabled`() {
         // given
@@ -278,4 +292,47 @@ internal class EnvoyEgressRoutesFactoryTest {
             defaultRoute.matchingOnPrefix("/")
         }
     }
+
+    @Test
+    fun `should add traffic splitting header for secondary weighted cluster`() {
+
+        val expectedHeaderKey = "test-header"
+        val routesFactory = EnvoyEgressRoutesFactory(SnapshotProperties().apply {
+            loadBalancing.trafficSplitting.headerName = expectedHeaderKey
+        })
+
+        val routeConfig = routesFactory.createEgressRouteConfig(
+            "client1",
+            weightedClusters,
+            false
+        )
+
+        routeConfig
+            .hasClusterThat("srv1-aggregate") {
+                assertNotNull(this)
+                assertNotNull(this!!.responseHeadersToAddList.find { it.header.key == expectedHeaderKey })
+            }.hasClusterThat("srv1") {
+                assertNotNull(this)
+                assertTrue(this!!.responseHeadersToAddList.isEmpty())
+            }
+    }
+
+    @Test
+    fun `should not add traffic splitting header if header key is not set`() {
+        val routesFactory = EnvoyEgressRoutesFactory(SnapshotProperties())
+        val routeConfig = routesFactory.createEgressRouteConfig(
+            "client1",
+            weightedClusters,
+            false
+        )
+
+        routeConfig
+            .hasClusterThat("srv1-aggregate") {
+                assertNotNull(this)
+                assertTrue(this!!.responseHeadersToAddList.isEmpty())
+            }.hasClusterThat("srv1") {
+                assertNotNull(this)
+                assertNotNull(this!!.responseHeadersToAddList.isEmpty())
+            }
+    }
 }