New head coach Andrea Pirlo has undertaken a squad overhaul since taking charge of the Bianconeri, with various players like Gonzalo Higuain, Miralem Pjanic, and Blaise Matuidi leaving in the summer transfer window.
On deadline day on Monday, winger Douglas Costa left for Bayern on loan.
Juve have subsequently replaced the Brazilian with talented winger Chiesa - a player that Pirlo had been keen to bring in since becoming boss.
The Italy international will sign for two years on at a cost of €10m, with the obligation for a further €40m to be paid to make the move permanent.
Chiesa will join the likes of Arthur Melo, Weston McKennie, and Dejan Kulesevski, all of whom recently made their debuts for the Serie A champions.
He made 34 appearances in the league last season for Fiorentina, scoring 11 goals and assisting a further six.