The 63-year-old man was treated by paramedics at a restaurant on The Entrance Road, at The Entrance for multiple stab wounds about 6pm yesterday.
He was airlifted to hospital in a serious condition.
A 40-year-old man, believed to be known to the victim, was arrested nearby at Long Jetty.
He was taken to Wyong Police Station, where police are continuing their enquiries.
A crime scene has been set up at the restaurant.
Police investigations are ongoing.