diff --git a/packages/vitest/src/node/pools/browser.ts b/packages/vitest/src/node/pools/browser.ts
index 524596bd1..f94f747d4 100644
--- a/packages/vitest/src/node/pools/browser.ts
+++ b/packages/vitest/src/node/pools/browser.ts
@@ -32,7 +32,8 @@ interface BrowserTask {
   files: FileSpecification[]
   method: 'run' | 'collect'
   // providers without a per-session mocker share a single mock registry
-  // and some of them cannot drive several pages, so the instance runs alone
+  // unless mocks go through the import map, and some of them cannot drive
+  // several pages, so the instance runs alone
   exclusive: boolean
   result: DeferPromise<void>
 }
@@ -234,7 +235,9 @@ export function createBrowserPool(vitest: Vitest): BrowserPool {
             project,
             files,
             method,
-            exclusive: !provider.mocker || !provider.supportsParallelism,
+            exclusive:
+              !provider.supportsParallelism ||
+              (!provider.mocker && !project.config.browser.importMapMocks),
             result: createDefer<void>(),
           }
         },