The 15-year-old, named by officers only as Declan, was last seen near Nelson Road in Edlington on Monday April 25, and has not been seen or heard from since.
Officers today appealed for information and issued a photo of the missing teenager.
A South Yorkshire Police spokesman said: “Officers are growing increasingly concerned for his welfare.
“He is described as white, around 5ft 7ins tall with a medium build and brown hair. He is believed to be wearing a black and gold cross hatched jacket.
“He is known to frequent the Hyde Park, Intake and Wheatley areas and is believed to visit the Bowlers Club on Silver Street, Doncaster.
“Have you seen him? Do you know where he might be?
“If you can help, please call 101 quoting incident number 411 of 25 April.”