The 19-year-old Croatia cap scored 10 goals in 29 league appearances as the Split outfit finished fifth in the 2012-13 Prva HNL season.
A statement published on Fiorentina's official website read: "Fiorentina announces it has acquired the rights to Ante Rebic on a five-year contract.
"The Croatian player has already made one appearance and scored once for his country's national team."
The Tuscan club posted a video chronicling Rebic's induction at the Stadio Artemio Franchi where he underwent a medical before signing his contract alongside general manager Sandro Mencucci.
He told Calcio Mercato: "I'm not scared of this new adventure, even if I know what kind of competition I am going up against."