Juve fans were upset by Cannavaro leaving for Real in 2006 when they were demoted for match-fixing, while other top players such as Alessandro Del Piero and Gianluigi Buffon stuck with the club for their season in the second tier.
A small group of fans have protested at recent matches against Cannavaro's return after club bosses admitted they were in talks with the 2006 European and World Player of the Year.
"I am sure I will be able to convince even the most sceptical fans thanks to my hard work, professionalism and passion with which I will approach this new adventure," the World Cup winner said.
"Fabio is a world champion, a Ballon d'Or winner and a great man in the dressing room," Juve sporting director Alessio Secco said in a bid to calm supporter unrest.
"During the summer of 2006 the club had to sell him for urgent economic reasons."
German media said the deal was worth around 29 million euro but the transfer was still up in the air despite weeks of talks, Werder's General Manager Klaus Allofs said.
"There are still open questions that must be discussed thoroughly," Allofs told reporters in Istanbul ahead of the UEFA Cup final on Wednesday against Ukraine's Shakhtar Donetsk.
