The 26-year-old was one of the standout performers in La Liga last season as Sevilla finished in fifth place and he helped the Andalusians claim the Europa League crown with victory over Benfica in May.
The former Schalke star's performances caught they eye of many of Europe's elite clubs and his father admitted earlier this week that he had offers from Barca, Real Madrid and Atletico, adding: "We'll decide after the World Cup."
However, Goal understands Barca have now stolen a march on their two domestic rivals by agreeing a deal ahead of the summer showpiece in Brazil, which starts next week.
New coach Luis Enrique met with sporting director Andoni Zubizarreta for more than two hours on Thursday to discuss transfer plans for the summer and with former Arsenal pair Cesc Fabregas and Alex Song both looking likely to return to the Premier League, Barca have acted fast to push through a deal for Rakitic.
Sevilla coach Unai Emery was resigned to losing the Swiss-born midfielder on Thursday. "I could understand if Rakitic leaves," he told Canal Plus. "In an ideal world, he would stay but I know he has several offers. If he leaves, we'll try and sign another Rakitic."
Rakitic, who is preparing for Croatia's World Cup debut against Brazil, will sign a five-year deal with the Catalan club and his release clause is to be set at €70m.
He is the second Croatian to sign for Barca this summer after the Blaugrana also brought in 17-year-old attacking midfielder Alen Halilovic from Dinamo Zagreb.