Neither the stabbing victim, who was taken to Southside Hospital in Bay Shore, or a person who was struck in the head with a metal pipe suffered serious injuries, police said. Neither was identified.
The incident began at about 11:45 p.m. outside East Islip Lanes on Montauk Highway and Greenwood Avenue, police said. They said the fight quickly escalated until more than 40 people were involved.
No one has been arrested in the incident, which remained under investigation Tuesday.
Video from the scene showed a large number of people, most of them appearing to be in their teens or early 20s, seated against a wall in the parking lot of the bowling alley being questioned by investigators.
Police said those interviews went on until the early morning Tuesday.