Police say it happened just after 10:00 p.m. in the 1700 block of West Juniata Street.
Witnesses say the tree fell on a group of people who were attending a block party in the area.
"We were sitting and heard something crack. They tried to run and the tree fell, and they were trapped," said Judy Henderson.
Officials say a 15-year-old boy, a 23-year-old-man and a 34-year-old woman were among the victims transported to Einstein Medical Center.
A fourth person was taken to Temple University Hospital.
First responders say the injuries appear to be minor.
