Malachie Matthie, aged 15, from Middleton, was last seen at Leeds General Infirmary shortly after midnight in the early hours of this morning, June 13.
He is described as black, 5ft 6ins and slim, with an afro hairstyle. He was last seen wearing blue jeans and a black hooded top.
Police said he has links to the Woodhouse and Meanwood areas of the city.
Acting Detective Inspector James Entwistle, of Leeds District CID, said: “We are very concerned for Malachie’s welfare and urgently need to trace him and check he is okay. We would like to hear from anyone who has seen him or who has any information on his current whereabouts.”
Anyone with information is asked to contact Leeds District CID via 101 quoting log number 19 of June 13.