The Serie A powerhouse have named ex- Azzurri boss Spalletti to lead the team until the end of the season.
Spalletti steps in for the Croatian manager, who was let go following the loss to Lazio recently.
The former boss came on board in March filling the shoes of Thiago Motta but exited following a seven-month stint following a string of eight matches without a victory.
Spalletti led Napoli to the Serie A title in 2022-23 then moving on to lead the Italian national team, after the team's failure to reach the 2022 World Cup under former boss Roberto Mancini.
He helped them qualify for Euro 2024 exiting in the last 16 stage against Switzerland.
However, Spalletti was sacked by Italy in June post a qualifying defeat against Norway, with the Azzurri at risk of missing out on a third consecutive World Cup.
Spalletti's managerial career includes Inter Milan, Roma, and Udinese in Serie A and won the Russian Premier League twice with Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus in the midweek 3-1 triumph over Udinese which left them seventh in Serie A - six points adrift of Napoli at the top after nine rounds.
In the Champions League, they sit 25th in the league phase, with one loss and two draws in their first three games.
