Giancarlo Giannini spent most of his childhood in the settlement of Pitelli (La Spezia). In 1952, Giannini and his family moved to Naples where he graduated in Electronic Engineering at the Alessandro Volta Technological State Technical Institute. During his teen years, he moved to Rome and studied and studied acting at the Silvio D'Amico National Academy of Dramatic Art.

Giannini interpreted a wide range of characters, often very different from each other: from the proletarian worker to the mafia boss, from the protagonist of Italian comedy films to that of more dramatic nature. He was also very active on television, as an actor, singer, and dancer.

During his long career, Giannini has worked with many of the best Italian directors; among these are Luchino Visconti, Sergio Corbucci, Lina Wertmüller, Mario Monicelli, Dino Risi, Alberto Lattuada, Nanni Loy, Tinto Brass and Franco Brusati. He has dubbed numerous famous foreign actors, including Al Pacino, Jack Nicholson, Michael Douglas, Gérard Depardieu, Jeremy Irons, Dustin Hoffman, Ian McKellen, Ryan O'Neal and Leonard Whiting.

He has won prestigious awards in Italy and abroad and was nominated for an Academy Award for Best Actor in 1977 for his performance in Lina Wertmüller's Pasqualino Settebellezze.