The Serie A powerhouse have chosen previous Azzurri manager Spalletti to take the helm until the end of the season.
The experienced coach takes over from the Croatian manager, who was let go post the Lazio setback recently.
Tudor had joined the club in March as Thiago Motta's replacement but exited following a seven-month stint after an eight-game winless streak.
Under Spalletti, Napoli clinched the Serie A championship in 2022-23 prior to assuming the Italy role, who had failed to qualify for the 2022 World Cup with Mancini at the helm.
Under his guidance, they made it to Euro 2024 exiting in the last 16 stage against 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.
Spalletti has also managed Inter Milan, Roma and Udinese in Serie A and lifted the Russian league trophy twice while at Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus during the 3-1 victory over Udinese on Wednesday which left them seventh in Serie A - six points behind leaders Napoli after nine games.
They are 25th in the league phase of the Champions League, with one loss and two draws in their first three games.
