Police were called to the eastbound carriageway of the road, on the overhead section close to Brighton Street and St Andrew’s Quay, around 7.30pm.
It is understood that the boy was one of a number of young people who were walking across the road, but none of the others have yet come forward.
Police want to speak to the group and anyone who saw either the young people or a grey Toyota Auris in the area.
Humberside Police said: "The boy’s family – who have asked that he is not named – are being supported by our officers and our thoughts are with them at this very difficult time."
Drivers faced long delays after the road was closed following the accident.
Anyone with information is asked to call 101.