Masked raiders threatened staff when they targeted a Chatham supermarket.
Two men wearing black masks demanded money from workers at the Co-op in Albert Road.
It is believed one of them might have been armed with a knife when they struck at about 7.30am on Thursday.
No one was injured but it is not known how much money was taken.
The raiders are described as white and in their 20s. One man was wearing dark trousers and a light top, while the other was wearing a dark top and trousers. The pair are thought to have escaped in a light or bright blue Ford Focus.
Anyone with information should call Medway Police on 01634 792474 or CrimeStoppers on 0800 555 111.