diff --git a/packages/jupyterlab-chat-extension/src/chat-commands/providers/user-mention.tsx b/packages/jupyterlab-chat-extension/src/chat-commands/providers/user-mention.tsx
index 97107df..201f3ae 100644
--- a/packages/jupyterlab-chat-extension/src/chat-commands/providers/user-mention.tsx
+++ b/packages/jupyterlab-chat-extension/src/chat-commands/providers/user-mention.tsx
@@ -54,7 +54,7 @@ class MentionCommandProvider implements IChatCommandProvider {
     // Build the commands for each user.
     const commands: ChatCommand[] = Array.from(this._users)
       .sort()
-      .filter(user => user[0].startsWith(match))
+      .filter(user => user[0].toLowerCase().startsWith(match.toLowerCase()))
       .map(user => {
         return {
           name: user[0],
diff --git a/ui-tests/tests/user-mention.spec.ts b/ui-tests/tests/user-mention.spec.ts
index d4e6d61..e170a40 100644
--- a/ui-tests/tests/user-mention.spec.ts
+++ b/ui-tests/tests/user-mention.spec.ts
@@ -124,4 +124,24 @@ test.describe('#collaborator-mention', () => {
       );
     }
   });
+
+  test('should not be case sensitive', async ({ page }) => {
+    const chatPanel = await openChat(page, FILENAME);
+
+    // Send a message from guest.
+    await sendMessage(guestPage, FILENAME, 'test');
+
+    const input = chatPanel
+      .locator('.jp-chat-input-container')
+      .getByRole('combobox');
+    const chatCommandName = page.locator('.jp-chat-command-name');
+
+    await input.pressSequentially('@JO');
+    await expect(chatCommandName).toHaveCount(2);
+    for (let i = 0; i < (await chatCommandName.count()); i++) {
+      expect(['@jovyan', '@jovyan_2']).toContain(
+        await chatCommandName.nth(i).textContent()
+      );
+    }
+  });
 });