The gunman opened fire into a crowd around 10 p.m., according to investigators.
Police said a 2-year-old boy was taken to the hospital in critical condition after being shot in the back.
The boy's 18-year-old mother was hit multiple times and is also in critical condition, according to police.
Investigators said a 14-year-old girl was also in critical condition after being shot.
A 25-year-old woman is among the injured. She was shot twice in the leg, along with a 42-year-old woman who was taken to the hospital with a graze wound to the arm, according to investigators.
Police believe a man in dark clothing stood about a half-block away and fired into the crowd. The group was having a birthday party for a man who died just a few days ago, police said.
Investigators said the group should not have been gathering due to the stay-at-home order that's in place during the COVID-19 pandemic.
"They should not have been gathering, although, that is not the issue here. The issue is we have a young child shot. That is serious," Philadelphia Police Deputy Commissioner Mel Singleton said. "The mother very young, also shot, and three other females shot and that is the issue here, and we need to locate any persons who did this and make sure we get any information that we can out of this situation."
No arrests have been made.