Brooklyn Jones, who lives in the BD7 area of the city, was last seen at school on Flockton Road at about 8.50am today (Monday).
He then left the school and headed towards the park in Flockton Road.
It is possible he may also have been in the Horton park area at about 3pm, possibly with a pink pushbike.
Detective Inspector Ryan Bragg, of Bradford District CID, said: “We are very concerned for Brooklyn, who is vulnerable, and would like to speak to anyone who may have seen him.
“He is a young child, both the police and his parents are very keen to find him and make sure he is OK, especially with cold weather settling in this evening.“
Brooklyn is described as white, 4ft and slim, with short, dark brown hair.
He was last seen wearing black trousers and a black ‘puffa’ style jacket.
Anyone who has seen Brooklyn is asked to contact Bradford CID on 101, referencing police log 431 of November 13.