The ex midfielder, who played for the Catalan club between 2004 and 2008, will replace Dutchman Jordi Cruyff, the son of Barca great Johan Cruyff, who left in June after two years in the role.
"Deco will be in charge of setting Barcelona's sporting philosophy and putting together the squad with the coach and the coaching and becoming head of the football section," the Spanish club said in a statement.
Barca, who claimed their 27th LaLiga title in the last campaign, said Deco and director of football Mateu Alemany would work together until the end of the close season despite the Spaniard formally leaving the club in June.
