He was known internationally for his biographical docudrama Sacco & Vanzetti (1971), which was nominated for the Palme d'Or, and the historical miniseries Marco Polo (1982), which won the Primetime Emmy Award for Outstanding Limited Series.

The director originally wanted him to play the part of Colonel Mathieu, leader of the French Army paratroopers and principal antagonist of the film.

Everyone is afraid, waiting for this Mathieu to show up, and when he appears, someone in the theater shouts, ‘It’s that jerk Montaldo, look!’ and the cinema breaks out with laughter.

He then directed the heist film Grand Slam (1967), which starred an international cast including Edward G. Robinson, Klaus Kinski, and Janet Leigh.

[2] His cinema career continued with Machine Gun McCain, a US-set gangster picture starring John Cassavetes as a convicted bank robber recruited to rob a mob-run Las Vegas casino.

The film was a widespread critical success, earning Montaldo his second Palme d'Or nod, and is credited with spreading awareness of the duo's story worldwide.

The series, which aired on NBC in the United States, was the first Western film or television production to be shot on-location in the People's Republic of China, including location shooting in the Forbidden City.

In 1987, he directed Control, an ensemble drama starring Burt Lancaster, Ben Gazzara, Kate Nelligan, Ingrid Thulin and Erland Josephson; and The Gold Rimmed Glasses, which was nominated for the Golden Lion at the Venice Film Festival.

In 2002, Montaldo was ascended a Cavaliere di gran croce (Knight's Grand Cross) of the Order of Merit of the Italian Republic.

In 2020, Fabrizio Corallo made the documentary Vera & Giuliano, about the private and professional life of the couple Montaldo died on 6 September 2023, at the age of 93.