It happened at Smith Playground at 25th Street and Snyder Avenue just after 7 p.m. Wednesday.
Witnesses told police the 18-year-old man was stabbed approximately 10 times in the back.
Officers took the teen to the hospital where he is listed in stable condition.
No arrests have been made.
It was not clear if the teen had robbed anyone of any items, or if the person who stabbed him was one of the people targeted.
Chopper 6 showed police activity on 25th Street between the playground and the U.S. Post Office.
Police say the investigation is ongoing.