The Black Cats have captured the 28-year-old Italy international for a reported €8 million fee on a four-year contract
The Italy international was a part of the Juventus side which has won successive Serie A titles in 2011-12 and 2012-13.
Howver, he has struggled to nail down a starting spot in Turin and decided to continue his career elsewhere, so will link up with fellow Italian Paolo Di Canio in England.
Giaccherini was also a part of Italy’s Confederations Cup squad, and netted in their 4-2 loss to Barzil and played his part in helping them finish third after beating Uruguay 3-2 on penalties in the third-place play-off match.
The midfielder has made a total of 14 appearances for his country netting twice and establishing himself as a regular member of Cesare Prandelli's squad.
The 28-year-old started his career at Cesena and has previously had spells on loan at Forli, Bellaria Igea and Pavia.