The news ends months of speculation over the former Arsenal's captain future and keeps him at Camp Nou until 2016.
In a short statement this morning, Barca said that his buyout clause is €200m (£175m). The reported transfer fee was €29m, with a further €5m if the side wins two leagues and a Champions League in the next five years. The Gunners will also receive €5m from Fabregas's wage packet over the period.
Arsenal and Barcelona confirmed last night that they had reached an initial agreement for the 24-year-old, who completed his two-stage medical this morning.
Fabregas, who was at Arsenal for eight years, is expected to make his debut in the second leg of the Spanish Super Cup on Wednesday night.