It happened just before 3 p.m. on the 2600 block of Kensington Avenue.
Officers say they were called to the scene for reports of a person with a weapon.
At the scene, police found a 16-year-old male stabbed once in his back. He was transported to St. Christopher's Hospital for Children, where he was placed in stable condition.
No arrests have been made and no weapons were recovered.
Authorities described the suspect as a man with a thin build wearing a black hoodie that had a white design.
The suspect was reportedly last seen heading westbound on Cumberland Street.
Anyone with information on this incident is asked to contact the police at 215-686-TIPS (8477).
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