Barry's deal with West Brom expired last month and he had drawn interest from Barcelona, PSG, Bayern, Manchester United and Juventus. British media had reported that Barry had undergone a medical with French Ligue 1 champions PSG before Barcelona stepped in at the last minute and convinced him to join the ranks at La Masia, the club's famed academy.
Had he of signed for club in England, West Brom would've been able to take the matter to a tribunal and negotiate a higher fee.
Birmingham-born Barry, who can play as a striker or on the right wing, has starred for England at youth level, scoring 10 goals in five games for the Under-15s at a tournament in Italy.
But it is Barça who have secured his signing and on Thursday made the announcement of the player who will now be part of the Juvenil A side having signed a three-year contract.
West Brom are yet to confirm Barry's departure.
Barry had been with the Baggies since the age of six but has recently turned down the offer of a professional contract with his boyhood club.