The robbery occurred at about 2:30 yesterday afternoon as three men entered the premises from the rear and relieved two females and a male employee of a till containing cash and stamps.
The value of the cash and stamps has not been confirmed.
According to the police, the gunmen made their escape in the direction of Brown's Gully and Stanton Road, two well-known hot spots in the parish capital.
The Morant Bay Police are investigating.