diff --git a/packages/vitest/src/node/cache/cachedirTag.ts b/packages/vitest/src/node/cache/cachedirTag.ts
new file mode 100644
index 000000000..e4e5dfb60
--- /dev/null
+++ b/packages/vitest/src/node/cache/cachedirTag.ts
@@ -0,0 +1,39 @@
+import { writeFileSync } from 'node:fs'
+import { join } from 'pathe'
+import { createDebugger } from '../../utils/debugger'
+
+const debug = createDebugger('vitest:cache:tag')
+
+// https://bford.info/cachedir/
+const CACHEDIR_TAG = `Signature: 8a477f597d28d172789f06886806bc55
+# This file is a cache directory tag created by Vitest.
+# For information about cache directory tags see https://bford.info/cachedir/
+`
+
+const taggedDirs = new Set<string>()
+
+/**
+ * Marks a directory that Vitest owns as a cache, so backup tools and task runners
+ * can skip it. An existing tag is never overwritten. The directory must exist.
+ */
+export function tagCacheDir(dir: string): void {
+  if (taggedDirs.has(dir)) {
+    return
+  }
+  taggedDirs.add(dir)
+  try {
+    writeFileSync(join(dir, 'CACHEDIR.TAG'), CACHEDIR_TAG, { flag: 'wx' })
+  } catch (error: any) {
+    // the tag is optional and must never fail the run
+    if (error?.code !== 'EEXIST') {
+      debug?.(`failed to tag ${dir} as a cache directory: ${error}`)
+    }
+  }
+}
+
+/**
+ * Tags the directory again the next time it is used, after it was removed.
+ */
+export function forgetCacheDirTag(dir: string): void {
+  taggedDirs.delete(dir)
+}
diff --git a/packages/vitest/src/node/cache/fsModuleCache.ts b/packages/vitest/src/node/cache/fsModuleCache.ts
index e20516f18..b1820f4b4 100644
--- a/packages/vitest/src/node/cache/fsModuleCache.ts
+++ b/packages/vitest/src/node/cache/fsModuleCache.ts
@@ -11,6 +11,7 @@ import c from 'tinyrainbow'
 import { searchForWorkspaceRoot } from 'vite'
 import { createDebugger } from '../../utils/debugger'
 import { hash } from '../hash'
+import { forgetCacheDirTag, tagCacheDir } from './cachedirTag'
 
 const debugFs = createDebugger('vitest:cache:fs')
 const debugMemory = createDebugger('vitest:cache:memory')
@@ -96,6 +97,7 @@ export class FileSystemModuleCache {
       ...this.vitest.projects.map((r) => r.config.fsModuleCachePath || this.rootCache),
     ]
     const uniquePaths = Array.from(new Set(fsCachePaths))
+    uniquePaths.forEach(forgetCacheDirTag)
     await Promise.all(
       uniquePaths.map((directory) => rm(directory, { force: true, recursive: true })),
     )
@@ -297,6 +299,7 @@ export class FileSystemModuleCache {
       if (!existsSync(cacheRoot)) {
         mkdirSync(cacheRoot, { recursive: true })
       }
+      tagCacheDir(cacheRoot)
     }
 
     const fsResultPath = join(cacheRoot, cacheKey)
@@ -330,6 +333,7 @@ export class FileSystemModuleCache {
       if (!existsSync(this.rootCache)) {
         mkdirSync(this.rootCache, { recursive: true })
       }
+      tagCacheDir(this.rootCache)
       await writeFile(this.metadataFilePath, JSON.stringify({ lockfileHash }, null, 2), 'utf-8')
     } catch (error) {
       // Recording the metadata is best-effort and losing the file shouldn't
diff --git a/packages/vitest/src/node/cache/results.ts b/packages/vitest/src/node/cache/results.ts
index 830cc9155..99b1b656d 100644
--- a/packages/vitest/src/node/cache/results.ts
+++ b/packages/vitest/src/node/cache/results.ts
@@ -5,6 +5,7 @@ import { existsSync } from 'node:fs'
 import { mkdir, readFile, rm, stat } from 'node:fs/promises'
 import { dirname, relative, resolve } from 'pathe'
 import { createDebugger } from '../../utils/debugger'
+import { tagCacheDir } from './cachedirTag'
 import { atomicWriteFile } from './fsModuleCache'
 
 const debug = createDebugger('vitest:cache:results')
@@ -199,7 +200,10 @@ export class ResultsCache {
     }
     const results: SerializedResults = { version: RESULTS_VERSION, projects }
     try {
-      await mkdir(dirname(this.path), { recursive: true })
+      const cacheDir = dirname(this.path)
+      await mkdir(cacheDir, { recursive: true })
+      // the cache is in "cacheDir/vitest/<hash>", Vitest owns the "vitest" directory
+      tagCacheDir(dirname(cacheDir))
       await atomicWriteFile(this.path, JSON.stringify(results))
       this.fileStamp = await getFileStamp(this.path)
     } catch (error) {
diff --git a/test/e2e/test/cachedir-tag.test.ts b/test/e2e/test/cachedir-tag.test.ts
new file mode 100644
index 000000000..04ad65c5f
--- /dev/null
+++ b/test/e2e/test/cachedir-tag.test.ts
@@ -0,0 +1,76 @@
+import { readFileSync } from 'node:fs'
+import { dirname, join } from 'pathe'
+import { expect, test } from 'vitest'
+import { runInlineTests } from '#test-utils'
+
+const SIGNATURE = 'Signature: 8a477f597d28d172789f06886806bc55'
+
+const passingTest = /* js */ `
+import { test } from 'vitest'
+test('passes', () => {})
+`
+
+function readTag(dir: string) {
+  return readFileSync(join(dir, 'CACHEDIR.TAG'), 'utf-8')
+}
+
+test('tags the results cache and the fs module caches', async () => {
+  const { ctx, root, stderr } = await runInlineTests(
+    {
+      'unit/basic.test.js': passingTest,
+      'api/basic.test.js': passingTest,
+      'vitest.config.js': {
+        test: {
+          fsModuleCache: true,
+          fsModuleCachePath: './node_modules/.vitest-fs-cache',
+          projects: [
+            { test: { name: 'unit', include: ['unit/*.test.js'] } },
+            {
+              test: {
+                name: 'api',
+                include: ['api/*.test.js'],
+                fsModuleCachePath: './node_modules/.vitest-api-cache',
+              },
+            },
+          ],
+        },
+      },
+    },
+    { cache: true },
+  )
+  expect(stderr).toBe('')
+
+  // the results are in "cacheDir/vitest/<hash>", Vitest owns "cacheDir/vitest"
+  const vitestCacheDir = dirname(ctx!.viteConfig.cacheDir)
+  expect(vitestCacheDir).toBe(join(root, 'node_modules/.vite/vitest'))
+  const tag = readTag(vitestCacheDir)
+  expect(tag).toMatchInlineSnapshot(`
+    "Signature: 8a477f597d28d172789f06886806bc55
+    # This file is a cache directory tag created by Vitest.
+    # For information about cache directory tags see https://bford.info/cachedir/
+    "
+  `)
+  expect(readTag(join(root, 'node_modules/.vitest-fs-cache'))).toBe(tag)
+  expect(readTag(join(root, 'node_modules/.vitest-api-cache'))).toBe(tag)
+})
+
+test('keeps an existing tag', async () => {
+  const customTag = `${SIGNATURE}\n# custom\n`
+  const { root, stderr } = await runInlineTests(
+    {
+      'basic.test.js': passingTest,
+      'node_modules/.vite/vitest/CACHEDIR.TAG': customTag,
+      'node_modules/.vitest-fs-cache/CACHEDIR.TAG': customTag,
+      'vitest.config.js': {
+        test: {
+          fsModuleCache: true,
+          fsModuleCachePath: './node_modules/.vitest-fs-cache',
+        },
+      },
+    },
+    { cache: true },
+  )
+  expect(stderr).toBe('')
+  expect(readTag(join(root, 'node_modules/.vite/vitest'))).toBe(customTag)
+  expect(readTag(join(root, 'node_modules/.vitest-fs-cache'))).toBe(customTag)
+})