Fix 0x80073b01 error installing Microsoft Teams — Defender block

Cause #1: Windows Defender real-time protection blocking Teams installation

This is the culprit 8 times out of 10. The 0x80073b01 error shows up when Windows Defender's real-time scanning interferes with the Teams installer mid-process. It's a false positive — Defender sometimes flags the Teams MSI or EXE as suspicious because of how it modifies registry keys during setup. I've seen this on Windows 10 22H2, Windows 11 23H2, and even Server 2022.

The fix is dead simple: disable real-time protection temporarily. Don't leave it off. Here's what to do:

1. Open Windows Security (search for it in the Start menu).
2. Click Virus & threat protection.
3. Under Virus & threat protection settings, click Manage settings.
4. Toggle Real-time protection to Off.
5. Run the Teams installer normally (right-click → Run as administrator).
6. Once Teams finishes installing, turn real-time protection back On.

That's it. If the error still pops up, move to cause #2.

Cause #2: Third-party antivirus (McAfee, Norton, Avast) blocking the installer

If you're running third-party antivirus, especially McAfee or Norton, those are just as aggressive as Defender. They'll kill the Teams install process mid-stream without telling you. Error 0x80073b01 is their favorite way to say "I don't like this file."

Don't bother uninstalling the AV. Just temporarily disable it:

• McAfee: Right-click the McAfee icon in the system tray → Disable Real-Time Scanning → select 15 minutes or 1 hour.
• Norton: Right-click the Norton icon → Disable Auto-Protect → choose 15 minutes.
• Avast: Right-click the Avast icon → Avast Shields Control → Disable for 10 minutes.
• Bitdefender: Open the main interface → Protection → turn off Advanced Threat Defense temporarily.

Then run the installer again. After it's done, re-enable the AV. If you're still stuck, go to cause #3.

Cause #3: Teams installer needs to be added as a Windows Defender exclusion

For enterprise environments or repeat offenders, you can't just disable Defender every time. The permanent fix is adding an exclusion for the Teams installer file or folder. This works even if you already tried disabling real-time protection — sometimes Defender still blocks the installer during a specific phase (like the registry write) despite the toggle.

Here's how to add an exclusion for the installer file:

1. Download the Teams installer again (TeamsSetup.exe or Teams.msi) to a known folder, like C:\Users\YourName\Downloads.
2. Open Windows Security → Virus & threat protection → Manage settings.
3. Scroll down to Exclusions → click Add or remove exclusions.
4. Click Add an exclusion → choose File.
5. Browse to the downloaded installer file and select it.
6. Run the installer as administrator.

If you deal with this across multiple machines in a domain, push the exclusion via Group Policy. Set this registry key on the client side:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths
Value Name: C:\Path\To\TeamsSetup.exe
Value Type: REG_DWORD
Value Data: 0

That tells Defender to ignore that specific file entirely. No more 0x80073b01.

Quick-reference summary table

One last thing — if none of this works, check if your Windows is fully updated. A fresh Windows Update (especially KB5036892 for Windows 11) has fixed Defender false positives for Teams in the past. But honestly? It's almost always one of the three above. You'll be fine.