Kai Myers, 11, was last spotted in Pudsey Park this afternoon, West Yorkshire Police said.
They are appealing for help to find the boy, who was wearing a grey and white Stanningley Rugby Club shirt.
Kai was also wearing a grey and black puffer jacket, school shoes and was carrying a Stanningley Rugby Club back with the initials "KM".
Anyone with information is asked to call police on 101 immediately.