Kayla Sample was last seen on June 22, troopers said in a release. Investigators believe she left her house in the middle of the night.
She is described as 5-foot-3 and 85 pounds with brown hair and brown eyes.
Anyone with information is asked to call the state police station in Embreeville at 610-486-6280.
Click here to follow Daily Voice West Chester and receive free news updates.