diff --git a/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts b/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
index fada9089d84f..538b891e1473 100644
--- a/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
+++ b/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
@@ -117,7 +117,8 @@ export async function createVitestConfigPlugin(
         test: {
           setupFiles,
           globals: true,
-          // Allow Vitest to manage test isolation by its default behavior.
+          // Default to `false` to align with the Karma/Jasmine experience.
+          isolate: false,
           sequence: { setupFiles: 'list' },
         },
         optimizeDeps: {