Jasmyn Barnes was last seen at about 2:30 p.m. walking away from the 700 block of Mountain View Street in the city of Altadena.
Sheriff's officials say she has left in the past and may be in the nearby Pasadena/Altadena area.
She is described as 5 feet 5 inches tall, about 120 pounds, with black hair in a ponytail and brown eyes. She was wearing a multi-colored jacket and gray pants.
Anyone with information about Jasmyn is encouraged to contact Altadena detectives at (626) 798-1131. If you prefer to provide information anonymously, you may call "Crime Stoppers" by dialing (800) 222 - TIPS (8477).