A teenager has been charged over an alleged assault at a Melbourne train station that left a man fighting for life.

A man in his 30s was left critically injured after the alleged attack at Craigieburn station on Hothlyn Drive about 4.20pm on Tuesday.

A man in his 30s was left critically injured after the attack at Craigieburn railway station on Hothlyn Drive. Credit:Nine News

Police said the victim and the teenager were involved in an altercation on a train shortly before the alleged assault in the bus bay area. It is believed that they did not know each other before the argument.

Transit Crime Investigation Unit detectives charged a 17-year-old boy on Tuesday night.

He has been charged with recklessly causing serious injury, committing an indictable offence while on bail and possessing a drug of dependence.

The victim was taken to Royal Melbourne Hospital in a critical condition, where he was treated for serious injuries to his upper body. He was in a serious condition on Wednesday morning.