diff --git a/src/card-controller/expand-manager.ts b/src/card-controller/expand-manager.ts
index 77db3416..6820a1d4 100644
--- a/src/card-controller/expand-manager.ts
+++ b/src/card-controller/expand-manager.ts
@@ -1,3 +1,4 @@
+import { setOrRemoveAttribute } from '../utils/basic';
 import { CardExpandAPI } from './types';
 
 export class ExpandManager {
@@ -28,6 +29,11 @@ export class ExpandManager {
 
     this._expanded = expanded;
     this._setConditionState();
+    setOrRemoveAttribute(
+      this._api.getCardElementManager().getElement(),
+      expanded,
+      'expanded',
+    );
     this._api.getCardElementManager().update();
   }
 
diff --git a/src/scss/card.scss b/src/scss/card.scss
index 766b88d4..cab7a493 100644
--- a/src/scss/card.scss
+++ b/src/scss/card.scss
@@ -36,8 +36,12 @@
 // from other cards. Tip: Best way to test this is with multiple Advanced Camera
 // Cards, opening a submenu on the 1st (e.g. media players) and verifying the
 // menu of the 2nd card is not visible through the opened submenu on the 1st.
-:host(:not(:hover)) {
-  z-index: #{$z-index-card-flatten};
+:host(:not(:hover):not([expanded])) {
+  z-index: auto;
+
+  // Create a new stacking context to prevent z-index issues with children
+  // "breaking out" of the card.
+  isolation: isolate;
 }
 
 advanced-camera-card-loading {
diff --git a/src/scss/z-index.scss b/src/scss/z-index.scss
index 18f26221..2d5139b4 100644
--- a/src/scss/z-index.scss
+++ b/src/scss/z-index.scss
@@ -18,6 +18,3 @@ $z-index-submenu: 5;
 $z-index-menu: 4;
 $z-index-drawer: 3;
 $z-index-status-bar: 2;
-
-// The base z-index when the card is not hovered over. See note in card.scss .
-$z-index-card-flatten: 0;
diff --git a/tests/card-controller/expand-manager.test.ts b/tests/card-controller/expand-manager.test.ts
index ad301c86..f1167378 100644
--- a/tests/card-controller/expand-manager.test.ts
+++ b/tests/card-controller/expand-manager.test.ts
@@ -1,7 +1,8 @@
 import { describe, expect, it, vi } from 'vitest';
 import { ExpandManager } from '../../src/card-controller/expand-manager';
-import { createCardAPI } from '../test-utils';
+import { createCardAPI, createLitElement } from '../test-utils';
 
+// @vitest-environment jsdom
 describe('ExpandManager', () => {
   it('should construct', () => {
     const api = createCardAPI();
@@ -19,6 +20,8 @@ describe('ExpandManager', () => {
 
   it('should set expanded', () => {
     const api = createCardAPI();
+    const element = createLitElement();
+    vi.mocked(api.getCardElementManager().getElement).mockReturnValue(element);
     vi.mocked(api.getFullscreenManager().isInFullscreen).mockReturnValue(true);
     const manager = new ExpandManager(api);
 
@@ -28,10 +31,13 @@ describe('ExpandManager', () => {
     expect(api.getFullscreenManager().setFullscreen).toBeCalledWith(false);
     expect(api.getConditionStateManager().setState).toBeCalledWith({ expand: true });
     expect(api.getCardElementManager().update).toBeCalled();
+    expect(element.hasAttribute('expanded')).toBeTruthy();
   });
 
   it('should not exit fullscreen when not in fullscreen', () => {
     const api = createCardAPI();
+    const element = createLitElement();
+    vi.mocked(api.getCardElementManager().getElement).mockReturnValue(element);
     vi.mocked(api.getFullscreenManager().isInFullscreen).mockReturnValue(false);
     const manager = new ExpandManager(api);
 
@@ -42,13 +48,45 @@ describe('ExpandManager', () => {
 
   it('should toggle expanded', () => {
     const api = createCardAPI();
+    const element = createLitElement();
+    vi.mocked(api.getCardElementManager().getElement).mockReturnValue(element);
     vi.mocked(api.getFullscreenManager().isInFullscreen).mockReturnValue(false);
     const manager = new ExpandManager(api);
 
     manager.toggleExpanded();
     expect(manager.isExpanded()).toBeTruthy();
+    expect(element.hasAttribute('expanded')).toBeTruthy();
 
     manager.toggleExpanded();
     expect(manager.isExpanded()).toBeFalsy();
+    expect(element.hasAttribute('expanded')).toBeFalsy();
+  });
+
+  it('should set expanded attribute on card element when expanded', () => {
+    const api = createCardAPI();
+    const element = createLitElement();
+    vi.mocked(api.getCardElementManager().getElement).mockReturnValue(element);
+    vi.mocked(api.getFullscreenManager().isInFullscreen).mockReturnValue(false);
+    const manager = new ExpandManager(api);
+
+    expect(element.hasAttribute('expanded')).toBeFalsy();
+
+    manager.setExpanded(true);
+
+    expect(element.hasAttribute('expanded')).toBeTruthy();
+  });
+
+  it('should remove expanded attribute on card element when collapsed', () => {
+    const api = createCardAPI();
+    const element = createLitElement();
+    vi.mocked(api.getCardElementManager().getElement).mockReturnValue(element);
+    vi.mocked(api.getFullscreenManager().isInFullscreen).mockReturnValue(false);
+    const manager = new ExpandManager(api);
+
+    manager.setExpanded(true);
+    expect(element.hasAttribute('expanded')).toBeTruthy();
+
+    manager.setExpanded(false);
+    expect(element.hasAttribute('expanded')).toBeFalsy();
   });
 });