The woman was walking on Oak Road, just north of Treat Boulevard, around 3:15 p.m. when she said she felt someone grab her, officials said.
The woman turned around and saw that it was a man that had been following her. The suspect released his grasp of the woman and then fled, according to officials.
Sheriff's officials and other law enforcement agencies searched for the suspect but did not find him, according to the sheriff's office.
The suspect is described as a white man, about 35 years old, standing 5 feet 10 inches, about 200 pounds and unshaven. He was seen wearing black slacks and a black dress shirt with a red tie.
Anyone with information about the suspect or case is encouraged to call the sheriff's office at (925) 646-2441.