The Old Lady have named former Italian national team boss Spalletti as their manager for the rest of the term.
The experienced coach takes over from Igor Tudor, who was let go after the Serie A side's defeat by Lazio on Sunday.
The former boss came on board in March filling the shoes of Thiago Motta but exited following a seven-month stint after an eight-game winless streak.
Spalletti led Napoli to the Serie A title in 2022-23 then moving on to lead the Italian national team, who had failed to qualify for the 2022 World Cup with Mancini at the helm.
He secured their spot in Euro 2024 but were eliminated in the round of 16 by Switzerland.
Nonetheless, Italy dismissed Spalletti in June following a loss to Norway in World Cup qualifying, with the Azzurri at risk of missing out on a third consecutive World Cup.
Spalletti's managerial career includes Inter Milan, Roma, and Udinese in Serie A and won the Russian Premier League twice with Zenit St Petersburg.
Juventus were temporarily led by Massimo Brambilla in the midweek 3-1 triumph over Udinese moving them to seventh position in the league - six points behind leaders Napoli after nine games.
Their Champions League campaign sees them in 25th place in the group stage, with one loss and two draws in their first three games.
