The Old Lady have named previous Azzurri boss the veteran manager to take the helm for the rest of the term.
The experienced coach steps in for his predecessor, who was let go following the loss to Lazio on Sunday.
Tudor had joined the club in March filling the shoes of Thiago Motta 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, which missed out on the 2022 World Cup during Roberto Mancini's tenure.
He secured their spot in Euro 2024 but were eliminated in the round of 16 by Switzerland.
However, Spalletti was sacked by Italy in June following a loss to Norway in World Cup qualifying, putting Italy in danger of missing a third straight World Cup.
Spalletti has also managed Inter Milan, Roma and Udinese in Serie A and secured two Russian Premier League titles with Zenit St Petersburg.
Massimo Brambilla served as interim manager for Juventus for their 3-1 win against Udinese on Wednesday placing them seventh in the Serie A standings - six points behind leaders Napoli after nine games.
In the Champions League, they sit 25th in the league phase, having lost once and drawn twice in their opening three matches.
