The midfielder, who turned 33 last Friday, agreed to extend his current deal by two years back in December, and has now officially put pen to paper to cement his future with the only club for which he has ever played. Xavi signed the deal at Camp Nou alongside Barca president Sandro Rosell, vice president Josep Maria Bartomeu and sporting director Andoni Zubizarreta.
Carles Puyol signed his own extension until 2016 on Jan. 22, but Lionel Messi is yet to make his commitment to the club - this time until 2018 - official.
The Blaugrana are preparing to face rivals Real Madrid in Wednesday night's Copa del Rey Clasico, and Xavi had earlier stated that Los Blancos should not be underestimated.
"These games are always unpredictable. We are really in good shape to compete right now but anything can happen in football, and particularly against Real Madrid," Xavi told reporters. "They will be missing a few important players, but they are Real Madrid after all and they will compete well, I'm sure. Despite their current situation, they are a dangerous opponent."