diff --git a/tests/setup.ts b/tests/setup.ts
index 6b81d53..2f8dae2 100644
--- a/tests/setup.ts
+++ b/tests/setup.ts
@@ -2,7 +2,9 @@
 // This file runs before all tests
 
 import { beforeAll, afterAll } from 'vitest';
-import { execSync } from 'child_process';
+import { execSync, execFileSync } from 'child_process';
+
+const isWindows = process.platform === 'win32';
 
 // Track if we're in cleanup mode
 let isCleaningUp = false;
@@ -17,7 +19,7 @@ afterAll(() => {
 });
 
 /**
- * Cleanup function to kill all Firefox and geckodriver processes
+ * Cleanup function to kill leftover test Firefox and geckodriver processes
  * This ensures no zombie processes are left after test runs
  */
 function cleanup() {
@@ -26,6 +28,15 @@ function cleanup() {
   }
   isCleaningUp = true;
 
+  if (isWindows) {
+    cleanupWindows();
+  } else {
+    cleanupUnix();
+  }
+  isCleaningUp = false;
+}
+
+function cleanupUnix() {
   try {
     // Find Firefox processes started with --marionette (test instances)
     const firefoxPids = execSync('pgrep -f "firefox.*marionette" || true', {
@@ -57,8 +68,57 @@ function cleanup() {
     console.log('✅ Global cleanup: All test Firefox processes terminated');
   } catch {
     // Ignore errors - processes might already be dead
-  } finally {
-    isCleaningUp = false;
+  }
+}
+
+/**
+ * Windows only. Retrieve all process ids matching the provided name and
+ * optional command line pattern.
+ */
+function findWindowsProcessIds(imageName: string, commandLinePattern?: string): number[] {
+  const filter = commandLinePattern
+    ? `Name='${imageName}' AND CommandLine LIKE '%${commandLinePattern}%'`
+    : `Name='${imageName}'`;
+  const script =
+    `Get-CimInstance Win32_Process -Filter "${filter}" | ` +
+    'Select-Object -ExpandProperty ProcessId';
+  const output = execFileSync(
+    'powershell.exe',
+    ['-NoProfile', '-NonInteractive', '-Command', script],
+    { encoding: 'utf-8', stdio: ['ignore', 'pipe', 'ignore'], windowsHide: true }
+  );
+  return output
+    .split(/\r?\n/)
+    .map((line) => line.trim())
+    .filter((line) => /^\d+$/.test(line))
+    .map(Number);
+}
+
+function cleanupWindows() {
+  try {
+    const firefoxPids = findWindowsProcessIds('firefox.exe', '--marionette');
+    for (const pid of firefoxPids) {
+      try {
+        // /T kills the whole process tree, replacing the Unix child-kill step
+        execSync(`taskkill /PID ${pid} /T /F`, { stdio: 'ignore' });
+      } catch {
+        // Ignore errors - process might already be dead
+      }
+    }
+
+    for (const pid of findWindowsProcessIds('geckodriver.exe')) {
+      try {
+        execSync(`taskkill /PID ${pid} /T /F`, { stdio: 'ignore' });
+      } catch {
+        // Ignore errors - process might already be dead
+      }
+    }
+
+    if (firefoxPids.length > 0) {
+      console.log('✅ Global cleanup: All test Firefox processes terminated');
+    }
+  } catch {
+    // Ignore errors - processes might already be dead
   }
 }