How to Fix Windows Defender Service Not Starting on Windows 11

Windows Defender is one of the most popular antivirus programs built-in every Windows device. It is better than most free antivirus available. The addition of sandboxing tools and cloud-based malware detection are some features it offers that aren’t included with many free antivirus programs.

It also includes a firewall and real-time virus defense that protects against ransomware by allowing users to access virtual folders so hackers cannot encrypt them. The Windows Defender can block unauthorized network traffic flowing in or out of the local device by providing host-based two-way network traffic filtering.

But recently, many users have been complaining about the Windows Defender service not starting on Windows 11. This error usually occurs due to some corrupt files present on your device. However, other issues may be responsible for this.

Keep reading this post to know how you can fix the Windows Defender service by not starting on Windows 11.

Also Read- Fix Windows 11 Mouse Not Working After Sleep

How to Fix Windows Defender Service Not Starting on Windows 11?

Fix 1: Restart your Device

Before starting with complex troubleshooting methods, we recommend to restart your device. Restarting your device can fix minor bugs and errors quickly.

Fix 2: Run SFC Scan

This error can also occur due to the presence of corrupted files on your system. Run an SFC or System File Checker scan to get rid of these corrupted files. Here is how you can do it:

1. Click on Start, search for Command Prompt and click on Run as Administrator.
2. Type the following command and hit enter.

   sfc/scannow

   

3. Close the Command Prompt, restart your device, and check if the Windows Defender service opens.

Fix 3: Delete Temporary Files

Errors like these can occur if your PC if too much temporary files are accumulated your device. These files get corrupt sometimes and cause various problems on your device. To fix this, delete all temporary files. Here is how you can do it:

1. Press the Windows key + R to open the Run dialog box.
2. Type %temp% and hit enter.
   
3. Press CTRL + A to select all temporary files.
4. Now press Shift + Del to delete all the files permanently.
   
5. Once done, restart your device and check if the issue is fixed.

Fix 4: Run a DISM Scan

System image corruptions are also known to cause issues like these. Run a DISM Scan to repair any system image corruptions on your device. Follow these steps to do so:

1. Click on Start, search for Command Prompt and click on Run as Administrator.
2. Type the following commands one by one and hit enter.

   DISM /Online /Cleanup-Image /CheckHealth 
   DISM /Online /Cleanup-Image /ScanHealth 
   DISM /Online /Cleanup-Image /RestoreHealth

   

3. Restart your device and check if the Windows Defender service not starting in Windows 11 issue is fixed.

Fix 5: Switch Account using Admin Profile

This error can also occur due to a lack of access permissions. To fix this, switch the user account using the admin profile. Here is how you can do it:

1. Press Windows key + R to open the Run dialogue box.
2. Type netplwiz and hit enter.
   
3. Choose the profile to modify and click on Properties.
   
4. Navigate to the Group Membership tab and select Administrator.
5. Click on Apply and then on Ok to save the changes.
   

Fix 6: Disable Third-Party Antivirus

Third-party antivirus software installed on your device can also cause this issue. Disable any antivirus software installed on your device and check if the windows defender service starts running.

If disabling the antivirus didn’t work, uninstall it temporarily and check for the same.

Fix 7: Set the Correct Environment Variable

The installation of third-party applications sometimes changes the value of Windows Environment Variables. This can also be the reason why Windows Defender is not working. You will have to check if the environment variables are set correctly to fix this. Here is how you can do it:

1. Click on Start, search for Advanced System Settings and select Open.
2. Navigate to the Advanced tab in the System Properties dialogue box.
3. Click on Environment Variables.
   
4. Check if the %ProgramFiles% is set to C: ProgramFiles. If not, edit the variable correctly.
   
5. Once done, click on Ok to save the changes.

Fix 8: Add a New User Account

If your existing user account gets corrupted for any reason, errors like these can occur. Add a new Microsoft account to fix this. Here is how you can do it:

1. Press Windows key + I to open Settings.
2. Click on Accounts > Family & other users.
   
3. Now click on Add Account under Other users.
   
4. A pop-up asking, “How this person will sign in?” will appear.
5. Click on I don’t have this person’s sign-in information.
   
6. Then select Add a user without a Microsoft account.
7. Add the username and set up the password on the next screen.
   
8. Now follow the instructions on the screen to create the new Microsoft user account.

Fix 9: Update Windows

You may be using an old update of Windows that may be causing this issue. Update to the latest build and check if the problem is fixed. Here is how you can do it:

1. Press Windows key + I to open Settings.
2. Click on Windows Update in the left pane.
3. Select Check for updates and follow the instructions on the screen to download and install the update.
   

Fix 10: Reset Windows

If none of those mentioned above steps could help you, factory reset your PC. Sometimes, the error is in the Windows core files that cannot be repaired manually. Here is how you can factory reset your PC:

1. Open Settings > Windows Update > Advanced Options > Recovery.
2. Finally, click on Reset this PC and follow the instructions on the screen.
   

Wrapping Up

That’s all on how you can fix the Windows Defender service not starting in Windows 11. We hope that the troubleshooting methods mentioned above were able to help you. If you still have any issues, feel free to drop a comment below.