The Old Lady have named former Italy manager Spalletti as their manager for the remainder of the campaign.
Spalletti steps in for Igor Tudor, who was sacked after the Serie A side's defeat by Lazio last weekend.
Tudor had joined the club in March as Thiago Motta's replacement but left after seven months after an eight-game winless streak.
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 with Mancini at the helm.
He secured their spot in Euro 2024 where they were knocked out in the last 16 by Switzerland.
Nonetheless, Italy dismissed Spalletti in June post a qualifying defeat against Norway, putting Italy in danger of missing a third straight World Cup.
Spalletti's managerial career includes Inter Milan, Roma, and Udinese in Serie A and secured two Russian Premier League titles with Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus for their 3-1 win against Udinese on Wednesday which left them seventh in Serie A - six points adrift of Napoli at the top after nine rounds.
They are 25th in the league phase of the Champions League, having lost once and drawn twice in their opening three matches.
