The incident happened Monday, Sept. 14 at about 8 p.m. in Port Jefferson Station, Suffolk County Police said.
Following a dispute involving three teenage boys, the victim, a 16-year-old, was stabbed multiple times on the soccer field behind Boyle Road Elementary School, located at 424 Boyle Road, police said.
The assailants then fled on foot on Bedford Avenue.
The victim was transported to a local hospital for treatment of serious injuries.
Detectives are asking anyone with information on the stabbing to contact the Sixth Squad at 631-854-8652 or Crime Stoppers at 800-220-TIPS.
All calls will remain confidential.
Click here to follow Daily Voice Massapequa and receive free news updates.