The 31-year-old arrived at Milan from Parma in 2006 and, despite several spells on the sidelines with injury, the former Italy international feels he still has much to contribute to the squad.
"I'm happy because I wanted to continue wearing this shirt," he told the club's official website.
"If I had the feeling I would only be here as a peripheral figure in the dressing room I would not have stayed.
"I really want to play and my experience will be of use to the young players, but I also want to win so much in this shirt.
"Milan are unique and will always be so. I'm happy to be a part of this club."