It was revealed on Thursday that the Black Cats had seen an offer for the Italy international accepted.
Juventus are reluctant sellers, as they prepare to part with a 28-year-old winger in his prime, but accept that he wants to find regular first-team football.
They cannot guarantee him that in Turin and have reluctantly sanctioned a sale to Sunderland.
Juve's general manager Giuseppe Marotta said: "In Giaccherini's transfer to Sunderland, the will of the player had priority over the club's.
"Emanuele evaluated, not only the economic aspects but also the standing he will have at Sunderland, and it was a challenge he decided to accept. We have gone along with his wishes."
Meanwhile, Marotta has revealed that Juventus have dropped their interest in Fiorentina forward Stevan Jovetic - who continues to be linked with the likes of Manchester City and Chelsea.
He added: "We have given up on Jovetic because with (Carlos) Tevez and (Fernando) Llorente we are satisfied with our attack.
"Jovetic was one of several targets but now he has become unattainable - not because we can't take him, but because we are proud of Tevez's arrival and think we have completed our attack."