The shooting was reported at 8:39 p.m. in the 1800 block of Eddy Street.
The girl was with her friends when she heard several shots, then felt a sharp pain in her right thigh and realized she had been shot, police spokesman Sgt. Daryl Fong said.
The girl was taken to San Francisco General Hospital to be treated for her injuries, which are not considered life-threatening. Fong said.
No one else was injured by the gunfire but a car parked nearby was also struck, he said.
No arrests have been made in the case and no suspect description was available today, Fong said.
Anyone with information about the shooting is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.