The 26-year-old will join the Blaugrana following the successful negotiation of a €20-million fee and has agreed a five-year deal to join Luis Enrique's side.
Rakitic, speaking ahead of his nation's vital World Cup encounter against Mexico, insisted he was completely focused on Croatia but was also looking ahead to his future with his new club.
"Moving to Barcelona is a big step in my career," the midfielder told a press conference.
"I want to thank Barca for being fair in the negotiations and satisfying Sevilla."
Rakitic has spent three-and-a-half years with Sevilla, scoring 32 goals in 149 games and lifting the Europa League trophy last season, and thanked los Rojiblancos for his time at the club.
"Sevilla is my club and I am very sad to leave," he continued.
"I had three wonderful years there in which I got married, had a daughter and had a great time personally."