Midland Detectives are appealing to for witnesses to the robbery, which occurred about 8.30pm at the PUMA service station at 604 Welshpool Road East.
Police say the offender walked to the address, entered the store and spoke to the attendant.
When the attendant turned to a cabinet behind the counter, the man went behind the counter, removing a beanie, plastic bag and knife from his pocket.
He allegedly threatened the attendant with the knife, stole money and left on foot.
Investigators believe the male in the photographs may be able to assist in the investigation.
He is described as having olive skin, dark, short curly hair, 175 to 180 centimetres, of medium build and in his mid 20s.
He was wearing a red zip up jacket, dark blue or black shorts and white shoes.
Anyone who can assist in identifying the male or provide any further information is asked to call Crime Stoppers on 1800 333 000.