The midfielder, who can also play up front and has one cap for his national team, has been at the Belgian club for six seasons.
Yakovenko was loaned out for two seasons to Westerlo and one at OH Leuven, both also in Belgium.
The Serie A club have now announced that they have signed Yakovenko on a three-year deal, where he will become only the fifth Ukrainian to play in the league, and the first for Fiorentina.
"The player last last season played with Royal Sporting Club Anderlecht," a statement on Fiorentina's official website read.
"Yakovenko signed a deal that will bound him to Viola club until 2016, June 30th."