Viola beat Bologna to Nakata
Bologna had hoped to sign the playmaker after a successful loan spell at the club last season, but Serie A new boys Fiorentina have beaten them to the punch.
Parma were resigned to losing Nakata as they look to ease their financial problems and they have accepted an undisclosed bid for the player.
The Viola moved quickly to tempt Nakata to the Artemio Franchi and he has signed a three-year deal at the club.
Fiorentina are Nakata's fifth club during his time in Italy after spells with Perugia, Roma, Parma and Bologna.
Nakata becomes Fiorentina's third new signing of the summer following the arrivals of Gianni Guigou and Cristiano Lupatelli.