Police believe the 19-year-old victim was at a licensed premises on Lonsdale Street when he was involved in an incident between two men just after midnight on June 8.
Officers have been told an unknown offender shoved the young man, in a crowded area of the venue, before it turned physical.
Police said a second unknown offender then approached the victim and smashed a glass in his face.
The North Melbourne teen suffered facial injuries and was taken to hospital for treatment.
The two offenders fled the scene along Elizabeth Street.
The first offender is described as being Caucasian in appearance, in his early twenties with shoulder-length dark hair.
He was last seen wearing a black t-shirt with a white jumper wrapped around his neck, blue jeans, black Adidas shoes with white stripes and a gold watch on his left wrist.
The second offender is described as being Caucasian in appearance, in his mid-twenties with short black hair.
He was last seen wearing a khaki jumper, black pants and black sneakers with a horizontal white stripe.