diff --git a/packages/browser/src/client/orchestrator.ts b/packages/browser/src/client/orchestrator.ts
index fe0d36050..6c49d73d5 100644
--- a/packages/browser/src/client/orchestrator.ts
+++ b/packages/browser/src/client/orchestrator.ts
@@ -78,7 +78,8 @@ export class IframeOrchestrator {
       await this.traces.flush()
     }
 
-    const startTime = performance.now()
+    // tester iframes have their own time origin
+    const startTime = performance.timeOrigin + performance.now()
 
     this.cancelled = false
 
diff --git a/packages/browser/src/client/tester/tester.ts b/packages/browser/src/client/tester/tester.ts
index f24ac7da0..cd9129212 100644
--- a/packages/browser/src/client/tester/tester.ts
+++ b/packages/browser/src/client/tester/tester.ts
@@ -152,7 +152,7 @@ if (isEmbedded) {
 
 let contextSwitched = false
 
-async function prepareTestEnvironment(options: PrepareOptions) {
+async function prepareTestEnvironment() {
   debug?.('trying to resolve the runner')
   const config = getConfig()
 
@@ -201,8 +201,6 @@ async function prepareTestEnvironment(options: PrepareOptions) {
     })
   }
 
-  state.durations.prepare = performance.now() - options.startTime
-
   return {
     runner,
     config,
@@ -257,17 +255,13 @@ interface PrepareOptions {
 }
 
 async function prepare(options: PrepareOptions) {
-  preparedData = await prepareTestEnvironment(options)
+  preparedData = await prepareTestEnvironment()
 
   // page is reloading
   debug?.('runner resolved successfully')
 
   const { config, state } = preparedData
 
-  state.durations.prepare = performance.now() - state.durations.prepare
-
-  debug?.('prepare time', state.durations.prepare, 'ms')
-
   setupEnv(config.env, state.metaEnv)
 
   await Promise.all([
@@ -282,6 +276,9 @@ async function prepare(options: PrepareOptions) {
     })(),
   ])
 
+  state.durations.prepare = performance.timeOrigin + performance.now() - options.startTime
+  debug?.('prepare time', state.durations.prepare, 'ms')
+
   if (!config.browser.trackUnhandledErrors) {
     getBrowserState().disposeExceptionTracker()
   }
diff --git a/test/browser/specs/prepare-duration.test.ts b/test/browser/specs/prepare-duration.test.ts
new file mode 100644
index 000000000..16353e035
--- /dev/null
+++ b/test/browser/specs/prepare-duration.test.ts
@@ -0,0 +1,43 @@
+import type { TestModule } from 'vitest/node'
+import { expect, test } from 'vitest'
+import { instances, runInlineBrowserTests } from './utils'
+
+test('prepareDuration does not include the time of previous files', async () => {
+  const testFile = `
+    import { test } from 'vitest'
+    test('waits', async () => {
+      await new Promise((resolve) => setTimeout(resolve, 1000))
+    })
+  `
+  const modulesByProject = new Map<string, TestModule[]>()
+
+  const { stderr } = await runInlineBrowserTests(
+    {
+      'first.test.ts': testFile,
+      'second.test.ts': testFile,
+    },
+    {
+      reporters: [
+        {
+          onTestModuleEnd(module) {
+            const modules = modulesByProject.get(module.project.name) ?? []
+            modules.push(module)
+            modulesByProject.set(module.project.name, modules)
+          },
+        },
+      ],
+    },
+  )
+
+  expect(stderr).toBe('')
+  expect(modulesByProject.size).toBe(instances.length)
+
+  for (const [project, modules] of modulesByProject) {
+    expect.soft(modules, project).toHaveLength(2)
+    const [previous, next] = modules.map((module) => module.diagnostic())
+
+    expect.soft(previous.prepareDuration, project).toBeGreaterThan(0)
+    expect.soft(next.prepareDuration, project).toBeGreaterThan(0)
+    expect.soft(next.prepareDuration, project).toBeLessThan(previous.duration)
+  }
+})