It happened around 9 p.m. inside the park at 54th and Lansdowne Avenue.
Police said six men and one woman were injured in the shooting. All the victims range in ages from 18 to 28 years old.
Investigators said two of the victims were struck in the head, another was struck two times near the stomach and the others suffered extremity wounds. They are all listed in stable condition at the hospital.
"We know that there was a basketball game inside this park along with several hundred other people having a party, and two males started firing," said Philadelphia Police Commissioner Richard Ross.
Neighbors of the park said they have become accustomed to these types of things happening.
"There are a lot of good people here but there are a lot of bad things happening," said Erma Jones.
Jones said when the shooting occurred her family was in the middle of celebrating her grandson's birthday.
"The kids were outside and they all came running in the house saying someone was shooting," she said.
Lataya Williams also heard the gunfire Saturday night, but said she, too, expected something like this to happen, adding there were around 200-300 people gathered at the park Saturday night.
"It's typical around here, this always happens," she said. "People get robbed, shot or house invasion."
Detectives were looking for surveillance video Sunday morning.
So far police believe there were two gunmen.
The motive is unclear at this point as to why this happened.
Anyone with any information is asked to call police at 215-686-TIPS.