Police officers on patrol were flagged down near Paradise Park, Holloway, shortly after 4.10pm on Wednesday.
A Metropolitan Police Service spokesman said further officers and London Ambulance Service were called to the scene after reports of a stabbing.
A teenager, believed to be 19 years old, was taken to an east London hospital.
His condition is not believed to be critical.
No arrests have been made and officers from Islington CID are continuing to investigate.
Anyone with information should call police on 101.