Microsoft Teams won't open on iMac

When did Teams last work on the affectied iMac? If this is the computer in your equipment line running macOS 13, that might be the issue. This MS article dated Sept 10 2025

https://learn.microsoft.com/en-us/microsoftteams/teams-client-system-requirements

has this OS requirement chart:

In Sept 2025, the "three most recent versions of macOS" became Tahoe v26, Sequoia v14, and Sonoma v14. OS 13 Ventura fell off the list.

If you are using an older version of Teams it might work, but yes, you need MS support on this.

If your Mac is running macOS 13 Ventura, Teams is no longer supported on it by Microsoft.

Jlamay71 wrote:

I have Microsoft Teams installed on my 6 yr. old iMac. Yesterday when I went to launch it, displayed an error message "This application cannot be opened". Any ideas about possible causes/solutions?

Look here https://support.microsoft.com/en-us/teams

KiltedTim wrote:

If your Mac is running macOS 13 Ventura, Teams is no longer supported on it by Microsoft.

FYI, I'm running the Teams app on Ventura with no problems. I just checked to see if there are any updates and I am still current with the most recent Feb. 2026 update to Teams according the MS updater. My MS Office is showing I can no longer receive updates, but Teams seems to be Ok for the moment. I guess I'll see how long this lasts. I know I must upgrade my OS before the end of the year, but still deciding on Sequoia, Tahoe, or wait & take the plunge with 27.x later this year.

I was even able to run the old Teams Classic on Big Sur up until about a year ago which surprised me since it had been abandoned for quite a while.