The incident took place around 1:45 a.m. at the Watutsi Lounge located in the 4600 block of Walnut Street.
According to police, two men were arguing inside and when they took the fight outside, one of the men pulled out a gun and began firing at the other.
There were several witnesses on the street when the shooter opened fire.
The victim, a man in his 20's was shot four times and rushed to the Hospital of the University of Pennsylvania in critical condition.
Two female bystanders, both in their 20's, suffered graze wounds. They were also taken to HUP, where they are expected to be treated and released.
So far, the gunman has not been identified or arrested.
The shooting remains under investigation.