It happened around 10 p.m. near 13th and Walnut streets.
Witnesses reportedly told police the stabbing took place after a fight.
The victims are said to be 19, 25, and 26 years old, and all are at the hospital.
Police say one of the victims was stabbed multiple times on his arms. Another was stabbed in the side and the third victim walked into the hospital with stab wounds on their arms.
Police say preliminary information indicates that one man and one woman began stabbing others.
"We're not sure of the motive at this time, whether it was random or whether it was provoked in some way or what the fight was about," said Chief Inspector D.F. Pace, with the Philadelphia Police Department. "We did receive some information though that some of the items that you see on this street, such as the canopy that was knocked down, that was also used as a possible weapon during this brawl in addition to the stabbing."
There is also no word on what may have sparked the initial fight.
Officials said there are many surveillance cameras in the area and police are working to review the footage.
No arrests have been made in this case. Anyone with information on this incident is asked to contact Philadelphia police.