The Old Lady have appointed former Italian national team manager the veteran manager as their manager for the remainder of the campaign.
Spalletti takes over from the Croatian manager, who was sacked post the Lazio setback on Sunday.
Tudor arrived at the club in March as Thiago Motta's replacement but exited following a seven-month stint at the end of an eight-match winless run.
Under Spalletti, Napoli clinched the Serie A championship in 2022-23 prior to assuming the Italy role, which missed out on the 2022 World Cup with Mancini at the helm.
Under his guidance, they made it to 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, putting Italy in danger of missing a third straight World Cup.
He has previously coached Inter Milan, Roma, and Udinese in Italy's top flight and secured two Russian Premier League titles with Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus in the midweek 3-1 triumph over Udinese moving them to seventh position in the league - six points adrift of Napoli at the top after nine rounds.
They are 25th in the league phase of the Champions League, with one loss and two draws in their first three games.
