Two men have been arrested after a man was allegedly attacked with a hammer and left fighting for life.

Police allege the victim, 41, was walking down Hoddle Street in Collingwood when he was set upon and attacked with a hammer about 4.30am.

The men, aged 18 and 19, from Fitzroy and Fitzroy North, were arrested on Friday morning.

The pair are assisting police and no charges have been laid yet.

The Collingwood man received life-threatening injuries remains in a critical condition in hospital.