A woman brandishing a syringe held up the United Service Station in Burnie.
Police say she threatened the male worker with a syringe, demanding money from the cash register.
The worker complied, and the female fled from the store with a quantity of cash.
He was treated for shock at the Burnie Hospital and discharged.
The incident happened between 5.30 and 6.30am.
Police say the woman was caught on the service station's CCTV and on street cameras, and are calling for any witnesses to contact Burnie police station on 64345211