Llorente is set to link up with the Serie A champions as a free agent when his contract at Bilbao expires in the summer.
"The future of Llorente is black and white," read a statement on Juve's official website.
"The Spain international, who will soon be out of contract at Athletic Bilbao, has signed an agreement that will bind him to Juventus from 1 July 2013. The contract, for a period of four years, will expire 30 June 2017.
"Until the end of this season the striker will continue to play for Athletic Bilbao."