Two brothers have handed themselves into police following a brutal assault on a train in Sydney's west.

Police released images of the two men on Tuesday afternoon after the assault of a 48-year-old man on the train home from a rugby league game at Sydney Olympic Park.

The incident occurred on Saturday night when the victim tried to intervene after he noticed two men arguing with a woman on the train, police said.

It is alleged one of the men then turned on the 48-year-old man and punched him in the face several times before he was held back by the second man and punched again.

Police said he fought back before other commuters intervened as the train approached Central Railway Station.

The men, wearing Penrith Panthers jerseys, then allegedly ran from the train.

CCTV footage showed the men taking their shirts off before exiting the station.

The 48-year-old man was taken to St Vincent’s Hospital and underwent plastic surgery for a laceration to his lip.

He also sustained a broken nose, two black eyes and a laceration to his forehead, police said.

Police said a 26-year-old man went to Penrith police station on Tuesday afternoon where he was arrested.

The man's brother, aged 28, then contacted police and was arrested at his house in Zetland.