How to Easily Fix Windows 11 Defender not Working (3 Ways)

You can learn 3 useful methods to fix Windows 11 Defender not working and the best way to protect computer from viruses or other threats. Keep reading to learn the detailed information.


by Clytze Updated on October 21, 2022

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Why Windows 11 Defender not Working?

Windows Security, commonly known as Windows Defender, is the default antivirus and security solution provided by Windows 11. It protects your software from viruses and malware. However, while using this software, many users are reporting that Windows Defender is not working in Windows 11.

Windows 11 Defender not working for several reasons. This article summarizes the common reasons as follows:

  • services not running.
  • presence of another security software.
  • a misconfigured date and time.
  • missing Windows updates.

How to Fix Windows 11 Defender not Working

To solve this Windows Security not working problem, this article introduces you to 3 useful methods to fix it. You can try these methods one by one, and I believe that there is always a method that will help you achieve the goal. And you can read on for more details.

Fix 1. Restart Security Center Service

Windows 11 Defender not working may be caused by the Security Center service in Windows 11 not running. To resolve this problem, you can follow the steps below to restart the Windows Security Center service to ensure that the service is running properly.

Step 1. Press Win + R to open the Run window, type services.msc and click OK to open Services page.

Step 2. In the right pane, find the Security Center service and select Restart.

Security Center Service 1


Just in case, you should also check these services: Windows Defender Advanced Threat Protection, Windows Defender Firewall, Windows Defender Antivirus Network Inspection Service, and Windows Defender Antivirus Service and make sure they are working properly.

Step 3. Double-click each service in turn to open the Properties window and set the Startup Type to Automatic. Once done, check if Windows Defender is working.

Fix 2. Disable Third-party Antivirus

If you have additional antivirus software installed on your computer, it may conflict with Windows Defender. If you want to run the Windows Defender app to keep your computer safe, you'd better disable or uninstall third-party antivirus software on your Windows 11 computer.

First, open Windows 11 Settings and go to Apps > Apps & Features. Then, search for antivirus software, and when you find it, click on the option (three dots) and select Uninstall. After uninstalling your antivirus software, restart your computer and try running Windows Defender to see if it works properly.

Unistall Third Party App

Fix 3. Run an SFC and DISM Scan

SFC, short for System File Checker, is a Windows tool you can rely on when some of your Windows files fail. It checks the file for corruption and then tries to fix it.

It can be accessed through the command prompt. To get started, go into the Start menu's search bar, type command prompt, and launch it as an administrator. This will launch your command prompt in elevated mode, which is necessary to run the SFC tool.

In the command prompt, enter the command below and hit enter. The tool will scan your computer and by the end, you should be able to run security applications.


SFC Scannow

If the SFC tool doesn't work, don't worry. You can also use another tool to help repair your computer, a DISM scan that can find and fix problems with the SFC tool. As with the SFC scan above, you must also start DISM as an administrator. When you start the DISM scan, enter the following command and hit enter.

DISM /Online /Cleanup-Image /ScanHealth

DISM Scanhealth

Once the command is executed, your files will be scanned and all corruption issues will most likely be resolved. When you're done, just restart your computer for the changes to take effect and see if the Windows Defender not working problem is fixed.

Fix 4. Reset Your PC

If none of the previous methods helped you solve the Windows Defender isn’t working problem, then you can try resetting your computer to its original state. Not only will this help you fix all kinds of problems with Windows, but it's much better than reinstalling Windows because you can choose to keep your files when you reset your computer. You can follow the steps below.

Step 1. Go to the Start menu search bar, type settings, and select the Best match.

Step 2. In the Settings menu, click on System > Recovery.

Step 3. In the Recovery options tab, click on Reset PC.

Reset This PC

Step 4. Then select Keep my files > Local reinstall and click on Next.

Follow the instructions and your PC will be reset. When your PC restarts, all your settings will be at ground zero again. 

Best Way to Protect Computer from Virus or Other Threats

By trying the above methods, I believe you have solved the problem of Windows 11 Defender not working. Now, you can run Windows Defender in Windows 11 normally to protect your PC from malware and virus threats.

But just running antivirus software won't completely protect your computer data. To prevent the system from being unable to boot or even losing data due to a virus attack, it is recommended to back up the system regularly. In this way, even if your system encounters any problems, you can quickly restore from the previously created system backup and use your system normally.

AOMEI Backupper Standard, a free and professional backup software, can help you easily set different frequencies to automatically back up your system regularly. You can also back up your system to various destinations according to your own needs. It supports a variety of Windows systems as well.

First, download AOMEI Backupper Standard, install and launch it. If you are a Windows Server user, you can select AOMEI Backupper Server.

Download Freeware Win 11/10/8.1/8/7/XP
Secure Download

Step 1. Open the software and click Backup > System Backup.

System Backup

Step 2. It will select system partition and boot-related partitions automatically. And you just need to select a destination.

Select Destination

Step 3. Click Start Backup to back up the Windows system.

Start Backup


  • Options: You can write comments, choose the compression level for your system backup or set email notifications.
  • Schedule Backup: This feature allows you to set the frequency of your backup, such as Daily, Weekly, Monthly, Event trigger and USB plug in. The professional version supports the last two features.
  • Backup Scheme: You can select 3 different backup methods (Full/Incremental/Differential), the differential backup method can easier to restore your scheduled backup task. You can upgrade to AOMEI Backupper Professional or higher versions to enjoy it.  


This article describes what Windows Defender does, why Windows 11 Defender not working and 3 ways to fix it. To better secure your computer data and avoid problems such as system failure caused by viruses or malware, it is recommended that you keep the habit of backing up your system regularly. This way, even if your system accidentally encounters any problem and fails to boot, you can use the previously created system backup for a quick restore.

The free backup software AOMEI Backupper Standard can automatically backup your system regularly according to the frequency you set. You can choose different backup paths and different Windows systems according to your own needs.

Besides, it is also an excellent restore software that not only helps you restore system backup quickly when you need it, but also restore system backup to computers with different hardware (Universal Restore). You can download this software to explore more useful features.

Clytze · Editor
Clytze, an editor at AOMEI Technology, is passionate about safeguarding your digital world. She dedicates her expertise to empower users like you in data security and recovery. She firmly believes that everyone should have the tools and knowledge to protect their digital assets through computer backup, seamless disk cloning, and efficient file synchronization. Clytze is your trusted guide on the journey to data safety.