diff --git a/.changes/20e287a5-cee0-4a5f-9d08-4022dcdee843.json b/.changes/20e287a5-cee0-4a5f-9d08-4022dcdee843.json
new file mode 100644
index 00000000000..37442f4cdd2
--- /dev/null
+++ b/.changes/20e287a5-cee0-4a5f-9d08-4022dcdee843.json
@@ -0,0 +1,5 @@
+{
+    "id": "20e287a5-cee0-4a5f-9d08-4022dcdee843",
+    "type": "misc",
+    "description": "Send x-amzn-query-mode=true for services with query-compatible trait"
+}
\ No newline at end of file
diff --git a/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/customization/AwsQueryModeCustomization.kt b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/customization/AwsQueryModeCustomization.kt
new file mode 100644
index 00000000000..1d97a3c7a08
--- /dev/null
+++ b/codegen/aws-sdk-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/customization/AwsQueryModeCustomization.kt
@@ -0,0 +1,28 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package aws.sdk.kotlin.codegen.customization
+
+import software.amazon.smithy.aws.traits.protocols.AwsQueryCompatibleTrait
+import software.amazon.smithy.kotlin.codegen.KotlinSettings
+import software.amazon.smithy.kotlin.codegen.integration.KotlinIntegration
+import software.amazon.smithy.kotlin.codegen.model.hasTrait
+import software.amazon.smithy.kotlin.codegen.rendering.protocol.MutateHeadersMiddleware
+import software.amazon.smithy.kotlin.codegen.rendering.protocol.ProtocolGenerator
+import software.amazon.smithy.kotlin.codegen.rendering.protocol.ProtocolMiddleware
+import software.amazon.smithy.model.Model
+
+/**
+ * Send an extra `x-amzn-query-mode` header with a value of `true` for services which have the [AwsQueryCompatibleTrait] applied.
+ */
+class AwsQueryModeCustomization : KotlinIntegration {
+    override fun enabledForService(model: Model, settings: KotlinSettings): Boolean =
+        model
+            .getShape(settings.service)
+            .get()
+            .hasTrait<AwsQueryCompatibleTrait>()
+
+    override fun customizeMiddleware(ctx: ProtocolGenerator.GenerationContext, resolved: List<ProtocolMiddleware>): List<ProtocolMiddleware> =
+        resolved + MutateHeadersMiddleware(extraHeaders = mapOf("x-amzn-query-mode" to "true"))
+}
diff --git a/codegen/aws-sdk-codegen/src/main/resources/META-INF/services/software.amazon.smithy.kotlin.codegen.integration.KotlinIntegration b/codegen/aws-sdk-codegen/src/main/resources/META-INF/services/software.amazon.smithy.kotlin.codegen.integration.KotlinIntegration
index 3ef264034df..6d8199d3072 100644
--- a/codegen/aws-sdk-codegen/src/main/resources/META-INF/services/software.amazon.smithy.kotlin.codegen.integration.KotlinIntegration
+++ b/codegen/aws-sdk-codegen/src/main/resources/META-INF/services/software.amazon.smithy.kotlin.codegen.integration.KotlinIntegration
@@ -43,3 +43,4 @@ aws.sdk.kotlin.codegen.customization.s3.express.S3ExpressIntegration
 aws.sdk.kotlin.codegen.customization.s3.S3ExpiresIntegration
 aws.sdk.kotlin.codegen.BusinessMetricsIntegration
 aws.sdk.kotlin.codegen.smoketests.SmokeTestsDenyListIntegration
+aws.sdk.kotlin.codegen.customization.AwsQueryModeCustomization
diff --git a/codegen/aws-sdk-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/customization/AwsQueryModeCustomizationTest.kt b/codegen/aws-sdk-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/customization/AwsQueryModeCustomizationTest.kt
new file mode 100644
index 00000000000..b8d5e3e67e3
--- /dev/null
+++ b/codegen/aws-sdk-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/customization/AwsQueryModeCustomizationTest.kt
@@ -0,0 +1,130 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package aws.sdk.kotlin.codegen.customization
+
+import aws.sdk.kotlin.codegen.testutil.lines
+import software.amazon.smithy.kotlin.codegen.test.*
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class AwsQueryModeCustomizationTest {
+    private val queryCompatibleModel = """
+        namespace com.test
+
+        use aws.protocols#awsJson1_0
+        use aws.protocols#awsQueryCompatible
+        use aws.api#service
+
+        @awsJson1_0
+        @awsQueryCompatible
+        @service(sdkId: "QueryCompatible")
+        service QueryCompatible {
+            version: "1.0.0",
+            operations: [GetFoo]
+        }
+
+        @http(method: "POST", uri: "/foo")
+        operation GetFoo {
+            input: GetFooInput
+        }
+        
+        structure GetFooInput {
+            payload: String
+        }            
+    """
+        .trimIndent()
+        .toSmithyModel()
+
+    private val nonQueryCompatibleModel = """
+        namespace com.test
+
+        use aws.protocols#awsJson1_0
+        use aws.protocols#awsQueryCompatible
+        use aws.api#service
+
+        @awsJson1_0
+        @service(sdkId: "NonQueryCompatible")
+        service NonQueryCompatible {
+            version: "1.0.0",
+            operations: [GetFoo]
+        }
+
+        @http(method: "POST", uri: "/foo")
+        operation GetFoo {
+            input: GetFooInput
+        }
+        
+        structure GetFooInput {
+            payload: String
+        }            
+    """
+        .trimIndent()
+        .toSmithyModel()
+
+    @Test
+    fun testEnabledForQueryCompatibleModel() {
+        assertTrue {
+            AwsQueryModeCustomization()
+                .enabledForService(queryCompatibleModel, queryCompatibleModel.defaultSettings())
+        }
+    }
+
+    @Test
+    fun testNotExpectedForNonQueryCompatibleModel() {
+        assertFalse {
+            AwsQueryModeCustomization()
+                .enabledForService(nonQueryCompatibleModel, nonQueryCompatibleModel.defaultSettings())
+        }
+    }
+
+    @Test
+    fun `x-amzn-query-mode applied`() {
+        val ctx = queryCompatibleModel.newTestContext("QueryCompatible", integrations = listOf(AwsQueryModeCustomization()))
+        val generator = MockHttpProtocolGenerator(queryCompatibleModel)
+        generator.generateProtocolClient(ctx.generationCtx)
+
+        ctx.generationCtx.delegator.finalize()
+        ctx.generationCtx.delegator.flushWriters()
+
+        val actual = ctx.manifest.expectFileString("/src/main/kotlin/com/test/DefaultTestClient.kt")
+
+        val getFooMethod = actual.lines("    override suspend fun getFoo(input: GetFooRequest): GetFooResponse {", "    }")
+
+        val expectedHeaderMutation = """
+            op.install(
+                MutateHeaders().apply {
+                    append("x-amzn-query-mode", "true")
+                }
+            )
+        """.replaceIndent("        ")
+
+        getFooMethod.shouldContainOnlyOnceWithDiff(expectedHeaderMutation)
+    }
+
+    @Test
+    fun `x-amzn-query-mode NOT applied`() {
+        val ctx = nonQueryCompatibleModel.newTestContext("NonQueryCompatible", integrations = listOf())
+        val generator = MockHttpProtocolGenerator(nonQueryCompatibleModel)
+        generator.generateProtocolClient(ctx.generationCtx)
+
+        ctx.generationCtx.delegator.finalize()
+        ctx.generationCtx.delegator.flushWriters()
+
+        val actual = ctx.manifest.expectFileString("/src/main/kotlin/com/test/DefaultTestClient.kt")
+
+        val getFooMethod = actual.lines("    override suspend fun getFoo(input: GetFooRequest): GetFooResponse {", "    }")
+
+        val unexpectedHeaderMutation = """
+            op.install(
+                MutateHeaders().apply {
+                    append("x-amzn-query-mode", "true")
+                }
+            )
+        """.replaceIndent("        ")
+
+        getFooMethod.shouldNotContainOnlyOnceWithDiff(unexpectedHeaderMutation)
+    }
+}