Corey Horner was last seen at his home in Milnsbridge, Huddersfield, on July 12.
He is described as white, 5ft 10ins tall, of slim build, with short, brown hair. He was last seen wearing a dark blue/black padded body warmer, navy jogging bottoms and black Adidas trainers.
Police are concerned for his welfare and a spokesperson urged Corey to "make contact with the police or his family to confirm he is safe and well".
Anyone who has seen Corey over the last few weeks or with information about his current whereabouts is asked to call Kirklees District Safeguarding Unit via 101, quoting log 794 of 13/07. Information can also be given by using the 101 Live Chat facility on the West Yorkshire Police website.