The central defender has rejoined the champions, after moving to Milan last July, as part of a deal that sees Gonzalo Higuain head the other way.
Juventus announced the signing on Thursday evening with a photo of Bonucci in the famous black-and-white and the messsage: ‘Welcome back, Bonucci.’
The swap will also sees 24-year-old defender Mattia Caldara head from Turin to the San Siro.
Bonucci has already been pictured in Juventus training gear, while Higuain has been spotted in Milan attire ahead of his initial loan move.
In a short statement on their website, Juventus confirmed that the defender arrived in Turin from Milan’s tour of the States on Thursday morning, before heading to the medical centre.
He completed his tests in the afternoon, with the deal virtually complete.
Bonucci’s return to Juve will reunite him with Andrea Barzagli and Giorgio Chiellini, who together formed the so-called ‘BBC’ defence, which proved to be one of Europe’s most formidable rearguards.
The 37-year-old Barzagli extended his contract for another season in June.