The Serie A powerhouse have appointed ex- Azzurri boss the veteran manager to lead the team for the remainder of the campaign.
The 66-year-old steps in for the Croatian manager, who was let go following the loss to Lazio recently.
Tudor arrived at the club in March filling the shoes of Thiago Motta but departed after seven months at the end of an eight-match winless run.
Spalletti guided Napoli to the Serie A crown in 2022-23 then moving on to lead the Italian national team, who had failed to qualify for 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 won the Russian Premier League twice with Zenit St Petersburg.
Massimo Brambilla took interim charge of 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.
They are 25th in the league phase of the Champions League, having lost once and drawn twice in their opening three matches.
