diff --git a/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html b/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html
new file mode 100644
index 0000000000..560e32604e
--- /dev/null
+++ b/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html
@@ -0,0 +1,111 @@
+<!doctype html>
+<html lang="en-US">
+  <head>
+    <link href="/assets/index.css" rel="stylesheet" type="text/css" />
+    <script crossorigin="anonymous" src="/test-harness.js"></script>
+    <script crossorigin="anonymous" src="/test-page-object.js"></script>
+    <!-- No React on the page: Web Chat uses the React DOM 16.8.6 it bundles. -->
+    <script crossorigin="anonymous" src="/__dist__/webchat-es5.js"></script>
+  </head>
+  <body>
+    <main id="webchat"></main>
+    <template id="outer-shadow-root">
+      <style>
+        #inner-host {
+          height: 100%;
+        }
+      </style>
+      <div id="inner-host"></div>
+    </template>
+    <template id="shadow-root-styles">
+      <link href="/assets/focusManagement.css" rel="stylesheet" type="text/css" />
+      <style>
+        /* Same as "body.jest input" in index.css, which does not reach into the shadow root: no blinking caret in snapshots. */
+        input {
+          caret-color: transparent;
+        }
+      </style>
+    </template>
+    <script type="importmap">
+      {
+        "imports": {
+          "@testduet/wait-for": "https://esm.sh/@testduet/wait-for"
+        }
+      }
+    </script>
+    <script type="module">
+      import { waitFor } from '@testduet/wait-for';
+
+      run(async function () {
+        const { directLine, store } = testHelpers.createDirectLineEmulator();
+        const outerShadowRoot = document.getElementById('webchat').attachShadow({ mode: 'open' });
+
+        outerShadowRoot.append(document.getElementById('outer-shadow-root').content.cloneNode(true));
+
+        const shadowRoot = outerShadowRoot.getElementById('inner-host').attachShadow({ mode: 'open' });
+
+        // `ShadowRoot.getRootNode()` returns the shadow root itself, however deep its host is nested.
+        expect(shadowRoot.getRootNode()).toBe(shadowRoot);
+
+        // GIVEN: Web Chat with React DOM 16.8.6 renders into a shadow root whose host is inside another shadow root.
+        WebChat.renderWebChat(
+          { directLine, store, styleOptions: { disableFileUpload: true, stylesRoot: shadowRoot } },
+          shadowRoot
+        );
+
+        // React empties the container when it first renders: add the styles after.
+        shadowRoot.append(document.getElementById('shadow-root-styles').content.cloneNode(true));
+
+        pageElements.root(shadowRoot);
+
+        await pageConditions.uiConnected();
+
+        // WHEN: The user types a message and presses ENTER.
+        const { activity: typedActivity, resolveAll: resolveTypedActivity } = await directLine.actPostActivity(
+          async () => {
+            await host.click(pageElements.sendBoxTextBox());
+            await host.sendKeys('Hello, World!', 'ENTER');
+
+            await pageConditions.numActivitiesShown(1);
+          }
+        );
+
+        await resolveTypedActivity();
+
+        expect(typedActivity).toHaveProperty('text', 'Hello, World!');
+        expect(shadowRoot.activeElement).toBe(pageElements.sendBoxTextBox());
+
+        // WHEN: The bot replies with a suggested action.
+        await directLine.emulateIncomingActivity({
+          suggestedActions: { actions: [{ title: 'USA', type: 'imBack', value: 'USA' }] },
+          text: 'Where are you from?'
+        });
+
+        await pageConditions.suggestedActionsShown();
+
+        // THEN: "Hello, World!" is sent, the bot asks "Where are you from?", the send box is empty and has the focus.
+        await host.snapshot('local');
+
+        // WHEN: The user clicks the suggested action.
+        const { activity: clickedActivity, resolveAll: resolveClickedActivity } = await directLine.actPostActivity(
+          async () => {
+            await pageObjects.clickNthSuggestedAction(1);
+            await pageConditions.numActivitiesShown(3);
+          }
+        );
+
+        await resolveClickedActivity();
+
+        expect(clickedActivity).toHaveProperty('text', 'USA');
+
+        await waitFor(() => expect(pageElements.suggestedActions()).toHaveLength(0));
+
+        // Clicking a suggested action moves the focus to the send box.
+        await waitFor(() => expect(shadowRoot.activeElement).toBe(pageElements.sendBoxTextBox()));
+
+        // THEN: "USA" is sent, the suggested action is gone and the send box has the focus.
+        await host.snapshot('local');
+      });
+    </script>
+  </body>
+</html>
diff --git a/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html.snap-1.png b/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html.snap-1.png
new file mode 100644
index 0000000000..cc78eb605b
Binary files /dev/null and b/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html.snap-1.png differ
diff --git a/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html.snap-2.png b/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html.snap-2.png
new file mode 100644
index 0000000000..fc74059d73
Binary files /dev/null and b/__tests__/html2/customElement/shadowRoot.interact.renderIntoNestedShadowRoot.html.snap-2.png differ
diff --git a/packages/bundle/src/renderWebChat.spec.tsx b/packages/bundle/src/renderWebChat.spec.tsx
index cac3e5975b..4177cbdc7d 100644
--- a/packages/bundle/src/renderWebChat.spec.tsx
+++ b/packages/bundle/src/renderWebChat.spec.tsx
@@ -114,6 +114,41 @@ describe('Element in a shadow root', () => {
   });
 });
 
+describe('Shadow root nested in another shadow root', () => {
+  let innerShadowRoot: ShadowRoot;
+
+  beforeEach(() => {
+    const innerHost = document.createElement('div');
+    const outerHost = document.createElement('div');
+
+    outerHost.attachShadow({ mode: 'open' }).append(innerHost);
+    document.body.append(outerHost);
+
+    innerShadowRoot = innerHost.attachShadow({ mode: 'open' });
+  });
+
+  afterEach(() => document.body.replaceChildren());
+
+  test('passed as the inner shadow root itself on React 16 should be rendered by ReactDOM.render()', () => {
+    // `ShadowRoot.getRootNode()` returns the shadow root itself, however deep its host is nested.
+    expect(innerShadowRoot.getRootNode()).toBe(innerShadowRoot);
+
+    renderWebChat(ReactWebChat, {}, innerShadowRoot);
+
+    expect(render).toHaveBeenCalledTimes(1);
+    expect(render.mock.calls[0][1]).toBe(innerShadowRoot);
+  });
+
+  test('with an element inside the inner shadow root on React 16 should throw', () => {
+    const element = document.createElement('div');
+
+    innerShadowRoot.append(element);
+
+    expect(() => renderWebChat(ReactWebChat, {}, element)).toThrow('on React 16 does not support');
+    expect(render).not.toHaveBeenCalled();
+  });
+});
+
 test('Element outside of a shadow root on React 16 should be rendered by ReactDOM.render()', () => {
   const element = document.createElement('div');