The teenager, Leon, was last seen in Sheffield on May 21 and has not been heard from since.
He is white, 5ft 5ins tall and slim.
Leon was last seen wearing a red T-shirt with black vertical stripes, a black parka coat and black bottoms.
Police officers in Doncaster have circulated his photograph in the hope that he is recognised.
Anyone with information on his whereabouts should call South Yorkshire Police on 101 and quote incident number 439 of May 21, 2022.