Belletti has been the only player not to see any action at the finals in the Far East so far, with Brazil boss Felipe Scolari preferring to use skipper Cafu in the right wing-back position.
The Primera Liga side acknowledged that the wing-back, who turns 26 on Thursday, agreed a five-year deal with the Estadio El Madrigal club.
At a press conference, Villarreal president Fernando Roig said: "We have reached an agreement for the transfer of the player and today we have received by fax the contract signed by Belletti."
The transfer of the talented but temperamental defender was reported to cost around £2.5million.
Belletti, who has 11 caps for his country, will have a ten-day break after the World Cup finals before joining his new team-mates in Spain, as Brazil face England in the quarter finals on Friday in Fukuroi.
