"The future of Fernando Llorente is black and white," Juve said in a statement on their website.
The 27-year-old Llorente, whose deal with Bilbao expires in June, has signed a contract with the Serie A side to June 2017 and will stay at Bilbao until the end of the season.
The powerful centre-forward, nicknamed the Lion King for his mane of blond hair, turned down the offer of a new contract with Bilbao during the close season and said he wanted to leave.
Bilbao initially refused to negotiate with interested parties and coach Marcelo Bielsa relegated last season's top-scorer to the bench, despite him having helped them to the 2012 Europa League and King's Cup finals by scoring 29 goals.
The Pamplona-born Llorente came up through Bilbao's youth academy before making his first-team debut in January 2005 and became their leading figure over the following seasons.
His relationship with some home fans has soured since his request to leave became public, and he has had to watch from the sidelines while new signing Aritz Aduriz has led the line for the side this season.
Llorente was a member of the Spain squad that won the World Cup in 2010 and Euro 2012, and has scored seven goals in 21 international appearances.
