[2] Giannini's international roles include the voice of Rat in the 2003 animated film Sinbad: Legend of the Seven Seas and Giancarlo Rossi in the 2012 ABC television series Missing, starring Ashley Judd and Sean Bean.

In 2024 he starred in two Netflix productions, playing Tommaso, Rocco Siffredi's half-brother, in the series Supersex and Ugo Jacomelli in the film Lonely Planet.

[3] Giannini has provided the Italian voices of Christian Bale, Tom Hardy, Raz Degan, Benicio del Toro, Steven Strait, Ryan Reynolds and Laz Alonso in some of their work[4] and the animated characters Metro Man in Megamind and Mandrake in Epic.

[5] Giannini had an older brother, Lorenzo, who died from an aneurysm at the age of 21.

He also has two younger half-brothers from his father's marriage to actress Eurilla del Bono.