Lara Snowie was last seen around 7 pm on Sunday April 4 in Dingwall.
The teen is described as around 5ft 6 inches tall, white with a local accent and a shaved head.
She was last seen wearing a grey puffer style jacket, purple "Nike" leggings, white "Nike" trainers and a yellow bobble- style hat with a pompom.
Inspector Goskirk from Dingwall Police Station said: “As the passage of time increases we are becoming very concerned for her welfare and it is imperative that we trace her current whereabouts as soon as possible so that we know she is safe.
"I would ask anyone who has seen Lara in the past 24 hours, or has any information on her whereabouts, to get in touch with officers immediately.”
Anyone with information should contact Police Scotland on 101 and quote incident number 3369 of April 4.