It happened around 7:30 p.m. Tuesday in the 3000 block of Salmon Street.
Police say it was there that the man, armed with a knife, approached the 17-year-old and tried to sexually assault her.
The attack apparently failed and the man fled on Indiana towards Richmond Street.
He is described as a black man about 30 to 40 years old standing about 6'2" tall. He also had a muscular build and a light beard, police said. He was wearing a black hooded sweatshirt with a gold zipper, blue jeans and dirty tan boots.
Anyone with information is asked to contact the Philadelphia Police Special Victims Unit at 215-685-3251 or submit a tip through the Philadelphia Police website.
