It happened around 6:30 p.m. Monday on the 2500 block of North 9th Street.
Authorities say the victim, Sameed Jenkins, had just walked out of the house and got on a bike, when he was struck by a stray bullet.
"This 11-year-old victim, who we believe of course is an innocent victim, was struck by a stray bullet," said Chief Inspector Scott Small, Philadelphia Police.
Sameed suffered a gunshot wound to the torso. He was taken to St. Christopher's Hospital in stable condition.
Police say the shots came from someone in a silver car, which was captured by surveillance cameras, fleeing the scene and heading south.
At about the same time, investigators say a 33-year-old male was shot in the 2700 block of Germantown Avenue.
That victim was struck in the stomach and the leg. He is listed in critical condition at Temple University Hospital.
Police believe the gunman was the same one driving the silver-colored vehicle. That same vehicle was later found with several bullet holes at 8th and Allegheny.
"We were lucky that there aren't additional children or adults that were shot. We know there were many, many people that were sitting outside when the shot rang out and struck this 11-year-old boy," said Chief Inspector Small.
Meanwhile, a relative of the 11-year-old victim says he is grateful that the boy's 4-year-old niece was not hit, as she was following him out the door to play.
"It's a tragedy and a shame that kids can't come out of the house without seeing gunfire coming from nowhere. It really don't make sense, they don't do anything to anybody. These crazy people out here who go buy guns and don't know how to use them, they get them for the wrong reasons," said Curtis Allen, uncle.
With the vehicle, believed to have been driven by the suspect, in their possession, police hope to quickly be able to make an arrest.