The Old Lady have appointed ex- Italy manager Spalletti as their manager for the rest of the term.
The experienced coach takes over from the Croatian manager, who was dismissed following the loss to Lazio recently.
Tudor arrived at the club in March as Thiago Motta's replacement but left after seven months after an eight-game winless streak.
Under Spalletti, Napoli clinched the Serie A championship in 2022-23 before taking charge of Italy, which missed out on the 2022 World Cup with Mancini at the helm.
He helped them qualify for Euro 2024 where they were knocked out in the last 16 by Switzerland.
Yet, the Italian FA let Spalletti go in June after a World Cup qualifying defeat by Norway, as Italy faced the possibility of not making a third World Cup in a row.
He has previously coached Inter Milan, Roma, and Udinese in Italy's top flight and lifted the Russian league trophy twice while at Zenit St Petersburg.
Juventus were temporarily led by Massimo Brambilla 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.
Their Champions League campaign sees them in 25th place in the group stage, after recording one defeat and two ties in the initial three fixtures.
