A man is fighting for his life in hospital after an alleged road-rage incident on the NSW mid north coast.

The man was assaulted during a fight with another man overnight at Dorrigo, about 40kms west of Coffs Harbour, said Detective Chief Inspector Jason Breton from Coffs Harbour police.

The victim was in a critical condition this morning at Coffs Harbour Base Hospital, he said.

The other man was being questioned by police.

No other details were yet available.