Napoli said that Bakayoko had joined Gennaro Gattuso’s side on a one-year deal, with club president Aurelio De Laurentiis saying “welcome Tiemoue” in the official statement.
Bakayoko, 26, will rejoin Gattuso after playing for the 2006 World Cup winner at AC Milan — also on loan from Chelsea — in the 2018/19 season.
He played for Monaco last season in another loan deal from the London club, where he is under contract until 2022.
Italian media report that Napoli will pay two million euros ($2.35 million) of his 3.5 million-euro annual salary.