The transfer fee remains undisclosed, although previous reports indicated that Nottingham Forest paid £12 million for the 26-year-old footballer.
Milenković has been with Fiorentina since 2017 and has made 57 appearances and scored 3 goals for the Serbian national team.
He becomes Nottingham Forest’s fifth signing of the summer, following the acquisitions of Elliot Anderson, Carlos Miguel, Marko Stamenic, and Eric da Silva Moreira.
Nottingham Forest narrowly avoided relegation last season, finishing 17th in the Premier League and fighting for survival until the final matchday.
