diff --git a/pages/content-layout/secondary-header-breakpoint.page.tsx b/pages/content-layout/secondary-header-breakpoint.page.tsx
new file mode 100644
index 0000000000..e8ff113d9a
--- /dev/null
+++ b/pages/content-layout/secondary-header-breakpoint.page.tsx
@@ -0,0 +1,84 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+import React, { useState } from 'react';
+
+import Box from '~components/box';
+import Button from '~components/button';
+import ContentLayout, { ContentLayoutProps } from '~components/content-layout';
+import FormField from '~components/form-field';
+import Header from '~components/header';
+import Select from '~components/select';
+import SpaceBetween from '~components/space-between';
+
+import { Containers } from '../app-layout/utils/content-blocks';
+import ScreenshotArea from '../utils/screenshot-area';
+
+const breakpointOptions: ReadonlyArray<{ value: ContentLayoutProps.SecondaryHeaderBreakpoint }> = [
+  { value: 'xxs' },
+  { value: 'xs' },
+  { value: 's' },
+  { value: 'm' },
+  { value: 'l' },
+  { value: 'xl' },
+];
+
+function QuickLaunch() {
+  return (
+    <Box padding="m">
+      <SpaceBetween size="s">
+        <Box variant="h3" padding="n">
+          Quick launch
+        </Box>
+        <SpaceBetween size="xs">
+          <Button fullWidth={true}>Launch instance</Button>
+          <Button fullWidth={true}>Create volume</Button>
+          <Button fullWidth={true}>View documentation</Button>
+        </SpaceBetween>
+      </SpaceBetween>
+    </Box>
+  );
+}
+
+export default function () {
+  const [breakpoint, setBreakpoint] = useState<ContentLayoutProps.SecondaryHeaderBreakpoint>('xs');
+
+  return (
+    <main>
+      <Box padding="m">
+        <FormField label="secondaryHeaderBreakpoint">
+          <Select
+            selectedOption={{ value: breakpoint }}
+            options={breakpointOptions}
+            onChange={({ detail }) =>
+              setBreakpoint(detail.selectedOption.value as ContentLayoutProps.SecondaryHeaderBreakpoint)
+            }
+          />
+        </FormField>
+      </Box>
+      <ScreenshotArea gutters={false}>
+        <ContentLayout
+          secondaryHeaderBreakpoint={breakpoint}
+          header={
+            <div style={{ padding: '20px 40px 0' }}>
+              <Header
+                variant="h1"
+                description="Adjust the breakpoint above to control when the secondary header stacks underneath the header."
+              >
+                Service homepage
+              </Header>
+            </div>
+          }
+          secondaryHeader={
+            <div style={{ padding: '20px 40px 0' }}>
+              <QuickLaunch />
+            </div>
+          }
+        >
+          <div style={{ padding: '0 40px 20px' }}>
+            <Containers />
+          </div>
+        </ContentLayout>
+      </ScreenshotArea>
+    </main>
+  );
+}
diff --git a/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap b/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap
index b54c1b56ab..d69d61d009 100644
--- a/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap
+++ b/src/__tests__/snapshot-tests/__snapshots__/documenter.test.ts.snap
@@ -10638,6 +10638,33 @@ If not set, all elements will occupy the full available width.",
       "optional": true,
       "type": "number",
     },
+    {
+      "description": "Determines the [breakpoint](/foundation/visual-foundation/responsive-design/) at and above which the \`secondaryHeader\`
+slot is displayed side-by-side with the \`header\` slot. Below this breakpoint, the secondary header stacks underneath
+the header and occupies the full available width.
+
+One of \`xxs\`, \`xs\`, \`s\`, \`m\`, \`l\`, or \`xl\`. Defaults to \`xs\`.
+
+Lower this value (for example, to \`xxs\`) to keep the header and secondary header side-by-side on narrow viewports,
+or raise it (for example, to \`s\` or \`m\`) to make them stack on wider viewports.
+
+This property has no effect unless both the \`header\` and \`secondaryHeader\` slots are set.",
+      "inlineType": {
+        "name": "ContentLayoutProps.SecondaryHeaderBreakpoint",
+        "type": "union",
+        "values": [
+          "s",
+          "m",
+          "xxs",
+          "xs",
+          "l",
+          "xl",
+        ],
+      },
+      "name": "secondaryHeaderBreakpoint",
+      "optional": true,
+      "type": "string",
+    },
   ],
   "regions": [
     {
diff --git a/src/content-layout/__tests__/content-layout.test.tsx b/src/content-layout/__tests__/content-layout.test.tsx
index 60a4fed801..16cb720e7c 100644
--- a/src/content-layout/__tests__/content-layout.test.tsx
+++ b/src/content-layout/__tests__/content-layout.test.tsx
@@ -4,6 +4,10 @@ import React from 'react';
 import { render } from '@testing-library/react';
 
 import ContentLayout, { ContentLayoutProps } from '../../../lib/components/content-layout';
+import {
+  defaultSecondaryHeaderBreakpoint,
+  getSecondaryHeaderGridDefinition,
+} from '../../../lib/components/content-layout/internal';
 import customCssProps from '../../../lib/components/internal/generated/custom-css-properties';
 import { useVisualRefresh } from '../../../lib/components/internal/hooks/use-visual-mode';
 import { highContrastHeaderClassName } from '../../../lib/components/internal/utils/content-header-utils';
@@ -64,6 +68,17 @@ function renderContentLayout(props: ContentLayoutProps = {}) {
         expect(wrapper.findSecondaryHeader()!.getElement()).toHaveTextContent('Secondary text');
       });
 
+      test('renders both header slots when secondaryHeaderBreakpoint is set', () => {
+        const { wrapper } = renderContentLayout({
+          header: <>Header text</>,
+          secondaryHeader: <>Secondary text</>,
+          secondaryHeaderBreakpoint: 'm',
+        });
+
+        expect(wrapper.findHeader()!.getElement()).toHaveTextContent('Header text');
+        expect(wrapper.findSecondaryHeader()!.getElement()).toHaveTextContent('Secondary text');
+      });
+
       test('does not render the secondaryHeader slot if the header slot is not present', () => {
         const { wrapper } = renderContentLayout({
           secondaryHeader: <>Secondary text</>,
@@ -282,3 +297,32 @@ function renderContentLayout(props: ContentLayoutProps = {}) {
     });
   });
 });
+
+describe('secondaryHeaderBreakpoint', () => {
+  test('defaults to the "xs" breakpoint', () => {
+    expect(defaultSecondaryHeaderBreakpoint).toBe('xs');
+  });
+
+  test('getSecondaryHeaderGridDefinition keeps the 9/3 split and full-width stacking below the breakpoint (default xs)', () => {
+    expect(getSecondaryHeaderGridDefinition(defaultSecondaryHeaderBreakpoint)).toEqual([
+      { colspan: { default: 12, xs: 9 } },
+      { colspan: { default: 12, xs: 3 } },
+    ]);
+  });
+
+  test.each(['xxs', 'xs', 's', 'm', 'l', 'xl'] as const)(
+    'getSecondaryHeaderGridDefinition applies the side-by-side split at the "%s" breakpoint',
+    breakpoint => {
+      expect(getSecondaryHeaderGridDefinition(breakpoint)).toEqual([
+        { colspan: { default: 12, [breakpoint]: 9 } },
+        { colspan: { default: 12, [breakpoint]: 3 } },
+      ]);
+    }
+  );
+
+  test('lowering the breakpoint to "xxs" keeps the slots side-by-side on narrow viewports', () => {
+    const [headerColumn, secondaryColumn] = getSecondaryHeaderGridDefinition('xxs');
+    expect(headerColumn.colspan).toEqual({ default: 12, xxs: 9 });
+    expect(secondaryColumn.colspan).toEqual({ default: 12, xxs: 3 });
+  });
+});
diff --git a/src/content-layout/interfaces.ts b/src/content-layout/interfaces.ts
index a48780bbad..4b717617eb 100644
--- a/src/content-layout/interfaces.ts
+++ b/src/content-layout/interfaces.ts
@@ -79,4 +79,22 @@ export interface ContentLayoutProps extends BaseComponentProps {
    * Note that the secondary header will not have a high-contrast treatement, even if you set `headerVariant` to `high-contrast`.
    */
   secondaryHeader?: React.ReactNode;
+
+  /**
+   * Determines the [breakpoint](/foundation/visual-foundation/responsive-design/) at and above which the `secondaryHeader`
+   * slot is displayed side-by-side with the `header` slot. Below this breakpoint, the secondary header stacks underneath
+   * the header and occupies the full available width.
+   *
+   * One of `xxs`, `xs`, `s`, `m`, `l`, or `xl`. Defaults to `xs`.
+   *
+   * Lower this value (for example, to `xxs`) to keep the header and secondary header side-by-side on narrow viewports,
+   * or raise it (for example, to `s` or `m`) to make them stack on wider viewports.
+   *
+   * This property has no effect unless both the `header` and `secondaryHeader` slots are set.
+   */
+  secondaryHeaderBreakpoint?: ContentLayoutProps.SecondaryHeaderBreakpoint;
+}
+
+export namespace ContentLayoutProps {
+  export type SecondaryHeaderBreakpoint = 'xxs' | 'xs' | 's' | 'm' | 'l' | 'xl';
 }
diff --git a/src/content-layout/internal.tsx b/src/content-layout/internal.tsx
index a021bb862a..45b265f4ea 100644
--- a/src/content-layout/internal.tsx
+++ b/src/content-layout/internal.tsx
@@ -5,6 +5,7 @@ import clsx from 'clsx';
 
 import { useCurrentMode, useMergeRefs } from '@cloudscape-design/component-toolkit/internal';
 
+import { GridProps } from '../grid/interfaces';
 import InternalGrid from '../grid/internal';
 import { getBaseProps } from '../internal/base-component';
 import customCssProps from '../internal/generated/custom-css-properties';
@@ -23,6 +24,20 @@ const halfGeckoMaxCssLength = ((1 << 30) - 1) / 120;
 // CSS lengths in Gecko are limited to at most (1<<30)-1 app units (Gecko uses 60 as app unit).
 // Limit the maxContentWidth to the half of the upper boundary (≈4230^2) to be on the safe side.
 
+export const defaultSecondaryHeaderBreakpoint: ContentLayoutProps.SecondaryHeaderBreakpoint = 'xs';
+
+/**
+ * Builds the grid definition for the header / secondary header split.
+ *
+ * The header spans 9 columns and the secondary header 3 columns (25%) at and above the provided
+ * breakpoint. Below the breakpoint both slots stack and occupy the full 12 columns.
+ */
+export function getSecondaryHeaderGridDefinition(
+  breakpoint: ContentLayoutProps.SecondaryHeaderBreakpoint
+): ReadonlyArray<GridProps.ElementDefinition> {
+  return [{ colspan: { default: 12, [breakpoint]: 9 } }, { colspan: { default: 12, [breakpoint]: 3 } }];
+}
+
 export default function InternalContentLayout({
   children,
   disableOverlap,
@@ -35,6 +50,7 @@ export default function InternalContentLayout({
   notifications,
   defaultPadding,
   secondaryHeader,
+  secondaryHeaderBreakpoint = defaultSecondaryHeaderBreakpoint,
   ...rest
 }: InternalContentLayoutProps) {
   const mainRef = useRef<HTMLDivElement>(null);
@@ -111,7 +127,7 @@ export default function InternalContentLayout({
             [styles['with-divider']]: headerVariant === 'divider',
           })}
         >
-          <InternalGrid gridDefinition={[{ colspan: { default: 12, xs: 9 } }, { colspan: { default: 12, xs: 3 } }]}>
+          <InternalGrid gridDefinition={getSecondaryHeaderGridDefinition(secondaryHeaderBreakpoint)}>
             <div className={clsx(testutilStyles.header, contentHeaderClassName)}>{header}</div>
             <div className={testutilStyles['secondary-header']}>{secondaryHeader}</div>
           </InternalGrid>