Mac: Microsoft Defender Update Error in Microsoft AutoUpdate

On macOS, Microsoft Defender for Endpoint can sometimes get stuck on an older version and fail to update through Microsoft AutoUpdate. The update window shows “Update error…” for Microsoft Defender, and clicking “Try Again” does not resolve the issue. This article explains how to fix the Defender update error using the official Microsoft upgrade helper tool.

Symptoms

• Microsoft AutoUpdate shows “Update error…” next to Microsoft Defender
• The current installed version of Defender is significantly behind the latest available version
• Clicking “Try Again” in Microsoft AutoUpdate does not resolve the error
• Other Microsoft 365 apps may update normally while Defender remains stuck

Cause

This issue occurs when the installed version of Microsoft Defender for Endpoint on macOS is too far behind the current release for the standard AutoUpdate mechanism to handle the upgrade. Older Defender versions (particularly those before certain major architecture changes) cannot apply incremental updates and require a manual upgrade path. Microsoft has documented this as a known issue and provides a dedicated upgrade helper tool to resolve it.

Resolution

Use the Microsoft Defender Upgrade Helper Tool

Microsoft provides an official upgrade helper script on GitHub that resolves this specific issue.

1. Visit the Microsoft Defender upgrade helper on GitHub
2. Download the upgrade helper script from the repository
3. Open Terminal on the Mac
4. Navigate to the folder where the script was downloaded
5. Run the script following the instructions provided in the GitHub repository (this typically requires administrator privileges)
6. Once the script completes, open Microsoft AutoUpdate and confirm that Microsoft Defender now shows as “Up To Date” or can update successfully

Alternative: Manually Reinstall Defender

If the upgrade helper does not resolve the issue, you can manually download and install the latest version of Microsoft Defender for Endpoint.

1. Download the latest Microsoft Defender for Endpoint installer from the Microsoft documentation
2. Run the installer package and follow the prompts
3. Restart the Mac after installation completes
4. Open Microsoft AutoUpdate and verify Defender is now on the latest version

Why This Matters

Microsoft Defender for Endpoint provides real-time threat protection on macOS devices. When Defender cannot update, the device is running outdated threat definitions and may miss new malware or security threats. Resolving update errors promptly ensures the Mac remains protected against the latest threats.

Key Takeaway

The Microsoft Defender “Update error” in Microsoft AutoUpdate on Mac is a known issue that occurs when Defender falls too far behind on updates. The official fix is to use the Microsoft upgrade helper tool from GitHub, which brings Defender back to a version that can accept normal updates. After running the tool, Defender should update normally through Microsoft AutoUpdate going forward.

Related Resources

• Fix: AirDrop Not Working on Intune-Managed Macs
• Fix: Business Application Blocked by Attack Surface Reduction (ASR) Rules

If you need help resolving Microsoft Defender issues on your Mac, get in touch with our team.