Detectives from the North-West Metro Serious Crime Taskforce are investigating following an armed robbery in Epping on Sunday.
Investigators have been told a man and women were walking in Derby Drive when an unknown man approached them about 9.45pm on 24 February.
The man pushed the 39-year-old woman to the ground before threatening the xx-year-old man with a knife.
He demanded cash before fleeing with their mobile phones and Apple watches.
Neither of the victims were injured during the incident.
Detectives have released a digital face image of a man they believe may be able to assist with their inquiries.
Anyone with information is urged to call Crime Stoppers Victoria on 1800 333 000 or log onto www.crimestoppersvic.com.au