The teenager was with a group of friends in Sandall Park when two men approached him at around 8.30pm last night. (Wednesday March 23)
The two men are then believed to have threatened the boy, demanding the keys to his motorbike before driving off on it.
South Yorkshire police said the suspects are both believed to have been carrying bladed weapons.
A police spokesman said: “No one was injured during the incident, but the victim and the rest of the group were understandably left extremely shaken.
The two men left the area on the bike, a white Kawasaki KE100, registration L79 MNW, towards Clay Lane.
One of the suspects is described as white, about 5ft 7ins tall, in his late teens and of slim build. He was wearing a black Nike baseball cap, a black Nike puffer coat, grey tracksuit bottoms and Nike Air Bubble trainers.
The second suspect is also described as white, about 18-years-old and of slim build with black hair. He was wearing a black Nike hooded top with black tracksuit bottoms.
Anyone with information is asked to call police on 101, quoting incident number 992 of 23 March 2016.
Or call Crimestoppers anonymously on 0800 555111.