diff --git a/src/middleware/timing/index.test.ts b/src/middleware/timing/index.test.ts
index ae5eed34f..527e73406 100644
--- a/src/middleware/timing/index.test.ts
+++ b/src/middleware/timing/index.test.ts
@@ -29,6 +29,12 @@ describe('Server-Timing API', () => {
     return c.text('cache!')
   })
 
+  const sub = new Hono()
+
+  sub.use(timing())
+  sub.get('/', (c) => c.text('sub'))
+  app.route('/sub', sub)
+
   it('Should contain total duration', async () => {
     const res = await app.request('http://localhost/')
     expect(res).not.toBeNull()
@@ -56,6 +62,16 @@ describe('Server-Timing API', () => {
     expect(res.headers.get('server-timing')?.includes(regionDesc)).toBeTruthy()
   })
 
+  it('Should not be enabled if the main app has the timing middleware', async () => {
+    const consoleWarnSpy = vi.spyOn(console, 'warn')
+    const res = await app.request('/sub')
+    expect(res.status).toBe(200)
+    expect(res.headers.has('server-timing')).toBeTruthy()
+    expect(res.headers.get('server-timing')?.includes(totalDescription)).toBeTruthy()
+    expect(consoleWarnSpy).not.toHaveBeenCalled()
+    consoleWarnSpy.mockRestore()
+  })
+
   describe('Should handle crossOrigin setting', async () => {
     it('Should do nothing when crossOrigin is falsy', async () => {
       const crossOriginApp = new Hono()
diff --git a/src/middleware/timing/timing.ts b/src/middleware/timing/timing.ts
index 5c76e826d..a221e8452 100644
--- a/src/middleware/timing/timing.ts
+++ b/src/middleware/timing/timing.ts
@@ -87,6 +87,11 @@ export const timing = (config?: TimingOptions): MiddlewareHandler => {
   return async function timing(c, next) {
     const headers: string[] = []
     const timers = new Map<string, Timer>()
+
+    if (c.get('metric')) {
+      return await next()
+    }
+
     c.set('metric', { headers, timers })
 
     if (options.total) {