diff --git a/.changeset/twelve-rules-glow.md b/.changeset/twelve-rules-glow.md
new file mode 100644
index 00000000000..2f6666688f2
--- /dev/null
+++ b/.changeset/twelve-rules-glow.md
@@ -0,0 +1,5 @@
+---
+'@itwin/itwinui-react': patch
+---
+
+iTwinUI will now also check for `vitest` and `mocha` (in addition to `jest`) before running any code that would cause problems in these test runners.
diff --git a/packages/itwinui-react/src/core/ThemeProvider/ThemeProvider.tsx b/packages/itwinui-react/src/core/ThemeProvider/ThemeProvider.tsx
index a6c7eb4dbca..df1a02cab5c 100644
--- a/packages/itwinui-react/src/core/ThemeProvider/ThemeProvider.tsx
+++ b/packages/itwinui-react/src/core/ThemeProvider/ThemeProvider.tsx
@@ -13,7 +13,7 @@ import {
   useControlledState,
   useLatestRef,
   importCss,
-  isJest,
+  isUnitTest,
 } from '../utils/index.js';
 import type { PolymorphicForwardRefComponent } from '../utils/index.js';
 import { ThemeContext } from './ThemeContext.js';
@@ -301,8 +301,8 @@ const FallbackStyles = ({ root }: { root: HTMLElement }) => {
       return;
     }
 
-    // bail if jest because it doesn't care about CSS 🤷
-    if (isJest) {
+    // bail if isUnitTest because unit tests don't care about CSS 🤷
+    if (isUnitTest) {
       return;
     }
 
diff --git a/packages/itwinui-react/src/core/utils/functions/dev.ts b/packages/itwinui-react/src/core/utils/functions/dev.ts
index 8ba8c76adb4..68c8db2a16a 100644
--- a/packages/itwinui-react/src/core/utils/functions/dev.ts
+++ b/packages/itwinui-react/src/core/utils/functions/dev.ts
@@ -2,14 +2,22 @@
  * Copyright (c) Bentley Systems, Incorporated. All rights reserved.
  * See LICENSE.md in the project root for license terms and full copyright notice.
  *--------------------------------------------------------------------------------------------*/
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
 const isJest = typeof (globalThis as any).jest !== 'undefined';
+const isMocha =
+  typeof (globalThis as any).beforeEach !== 'undefined' &&
+  `${(globalThis as any).beforeEach}`.replace(/\s/g, '') ===
+    'function(name,fn){suites[0].beforeEach(name,fn);}';
+const isVitest = typeof (globalThis as any).__vitest_index__ !== 'undefined';
+
+const isUnitTest = isJest || isVitest || isMocha;
 
 let isDev = false;
 
 // wrapping in try-catch because process might be undefined
 try {
-  isDev = process.env.NODE_ENV !== 'production' && !isJest;
+  isDev = process.env.NODE_ENV !== 'production' && !isUnitTest;
 } catch {}
 
 /**
@@ -31,4 +39,4 @@ const createWarningLogger = !isDev
       };
     };
 
-export { isJest, isDev, createWarningLogger };
+export { isUnitTest, isDev, createWarningLogger };