It happened around 6:30 p.m. at 54th Street and Springfield Avenue.
Police say a man and woman exited a car and were walking when they were approached by a masked man.
The man demanded the woman's purse, which contained an unspecified amount of money.
As the thief was taking the woman's purse, he shot the man, described as the woman's brother, in the shoulder.
The gunman then fled on foot.
The victim was rushed by medics to the Hospital of University of Pennsylvania for treatment. He is said to be stable.
Police say the woman belonged to an investment club and was toting some of that money when she was robbed.