Detectives from Stonnington Crime Investigation Unit are appealing for information following a series of three linked robberies last week.
Police have been told a man entered a convenience store on Dandenong Road, Windsor, around 2.45am on 11 August.
The man threatened the staff member and made demands, before running from the store with an amount of cash and cigarettes.
He was last seen running along Dandenong Rd
It is believed the same man, at about 4am, entered a service station store on Toorak Road in Toorak.
He again fled the store with a small amount of cash after threatening the staff member.
Less than 20 minutes later, at about 4.20am the man entered another convenience store on Victoria Avenue, Albert Park, and made demands to the staff.
On this occasion the staff member refused his demands and the bandana-wearing offender left the store empty handed.
The man is described as early to mid 20s, Caucasian in appearance, with brown hair and a medium build.
He was wearing black shoes, black pants, a black hooded jumper and green gloves.
Detectives have released an image of a man they believe can assist in their enquiries.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au