Masked thugs threatened staff at Farmfoods before stealing a key.
The three men walked into the Wythenshawe Civic Centre supermarket on Saturday (June 6) at around 6pm.
They threatened a staff member inside the shop.
A key was then taken.
The men fled the supermarket towards the nearby tram stop.
No one has been arrested.
A spokesman for Greater Manchester Police said: "At around 6pm on Saturday, June 6, 2020 police were called to a report of a robbery at a store at Wythenshawe Civic Centre.
"Three masked men entered the store and threatened an employee.
"A key was taken by one of the offenders before all three men fled the scene towards the nearby Metrolink station."
Anyone with further information can contact GMP on 101 or Crimestoppers, anonymously, on 0800 555 111.
