Police are appealing for information to help find a boy "despite extensive searches".
Officers are looking for 13-year-old Nathan Ilunga, who was last seen on South Promenade, Withernsea, at around 3.20pm on Friday.
Humberside Police said that "despite extensive searches, we have not been able to trace him".
He has links to London and the Thames Valley area, so he may have attempted to travel south.
He was last seen wearing a black North Face baseball cap, a two-tone grey puffa jacket, olive green tracksuit bottoms and black Nike trainers.
Nathan is 5ft 4ins tall and slim.
Police are asking anyone who can help to call 101, quoting log 387 of March 23.