The Serie A powerhouse have named previous Italy head coach the veteran manager to lead the team for the rest of the term.
Spalletti steps in for the Croatian manager, who was let go following the loss to Lazio last weekend.
Tudor had joined the club in March as Thiago Motta's replacement but departed after seven months at the end of an eight-match winless run.
Under Spalletti, Napoli clinched the Serie A championship 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 after a World Cup qualifying defeat by Norway, with the Azzurri at risk of missing out on a third consecutive World Cup.
Spalletti has also managed Inter Milan, Roma and Udinese in Serie A and won the Russian Premier League twice with Zenit St Petersburg.
Massimo Brambilla served as interim manager for Juventus during the 3-1 victory over Udinese on Wednesday moving them to seventh position in the league - six points adrift of Napoli at the top after nine rounds.
In the Champions League, they sit 25th in the league phase, after recording one defeat and two ties in the initial three fixtures.
