The Serie A powerhouse have appointed ex- Azzurri boss the veteran manager to take the helm until the end of the season.
The 66-year-old replaces the Croatian manager, who was sacked after the Serie A side's defeat by Lazio last weekend.
Tudor had joined the club in March as Thiago Motta's replacement but departed after seven months following a string of eight matches without a victory.
Spalletti led Napoli to the Serie A title in 2022-23 prior to assuming the Italy role, which missed out on the 2022 World Cup during Roberto Mancini's tenure.
Under his guidance, they made it to Euro 2024 exiting in the last 16 stage against Switzerland.
However, Spalletti was sacked by Italy in June following a loss to Norway in World Cup qualifying, as Italy faced the possibility of not making a third World Cup in a row.
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 served as interim manager for Juventus in the midweek 3-1 triumph over Udinese placing them seventh in the Serie A standings - trailing leaders Napoli by six points after nine matches.
In the Champions League, they sit 25th in the league phase, having lost once and drawn twice in their opening three matches.
