Transit Crime Investigation Team detectives are investigating a series of sexual assaults on trams this year.
Investigators have been told a man has allegedly committed the sexual assaults on three separate occasions on 28 February, 6 June and 18 August.
The offences occurred on the number 19A tram and the number 96 tram on two occasions.
Investigators have released images of a man they believe may be able to assist with their enquiries.
The man is perceived as being Southern European in appearance, medium build with receding dark hair.
Any witnesses or anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.