Rakitic, 32, left Sevilla six seasons ago for Barcelona and went on to win four La Liga titles and the Champions League.
He never hid his desire to return ‘home’ to Sevilla one day and has now achieved that dream.
Sevilla will pay just €1.5m for Rakitic, but Barcelona could up to €9m in variables.
Croatian midfielder Rakitic was one of those informed that they have no future at Camp Nou under Ronald Koeman.
In his previous spell with Sevilla, Rakitic scored 32 goals and delivered 41 assists in 149 games.
He leaves Barcelona after making 310 appearances, in which he clocked up 35 goals and 42 assists.