South Gate police said the teen was attacked in the 3400 block of Liberty Boulevard near the corner of Elizabeth Avenue.
The suspect description is similar to at least three other attacks in South Gate, police said. The victims range in age from 8 to 28.
Police say the attacks have gone from groping to a sexual assault.
The suspect was described as a male Hispanic in his 20s. He is about 5 foot, 4 inches to 5 foot, 8 inches, thin build, with short dark hair and brown eyes. He was wearing a dark hooded sweatshirt and black pants at the time of the attack.