Investigators were told the 23-year-old had been travelling on route 70 to Melbourne’s CBD on July 25 and boarded the tram at about 7pm outside Flinders Street Railway Station with family and friends.
The tram was heavily congested due to an event in the city and the victim initially stood face to face with the male suspect.
However, according to police, the man moved around the victim before he sexually assaulted her.
The woman tried to move away but was unable to remove herself from the situation immediately because of the limited space in the carriage.
Police said the man continued to assault her before she was eventually able to push herself away and tell her friends and family.
The man fled at William Barrack Bridge, after also being called out by an unknown commuter.
“It’s predatory, vile behaviour and he needs to be caught,” Detective Sergeant Michael Norris said on Sunday.
Detective Sergeant Michael Norris said the victim and her friends – and the offender – allowed a few trams to pass before boarding this particular one, as it was a busy night.
“So at what stage the offender has decided to target her, we don’t know,” Detective Sergeant Norris said.
The man is said to have distinctive gold capped teeth and a shaved head.
He is believed to be in his 50s or 60s and is described as being of Indian sub continental or African appearance.
Police said he is also said to have had piercing green eyes and had been well dressed, wearing business attire and a camel coloured trench coat.
Police have released a composite image of a man they believe can assist with their inquiries into the assault.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au
— Victoria Police (@VictoriaPolice) November 18, 2018