The boy, who has not been named yet, was last seen leaving Newquay's sports centre on his own at around 3pm. He was wearing a red Manchester United tracksuit top, football socks and white football boots.
Police have declared the incident high risk due to the boy's age and are appealing for information.
Anyone with information is asked to call 999 and to quote crime reference 04/16/03.
More top news
A young mum wants to find a stranger who left her a handwritten note, describing her as a "credit to her generation" and a five pound note
Conspiracy theorists claim this picture shows a "human-like being" fixing Nasa's Curiosity Rover on the surface of Mars.
The Brit actor has already won a Golden Globe and now a Screen Actor Guilds Award - which is widely known for predicting Oscar success.