Born in Rome, Colizzi started his career on stage at 17 years old,[1] then he graduated at the Accademia Nazionale d'Arte Drammatica Silvio D'Amico and in 1960 he got his first major role, playing the title role in an Italian TV adaptation of Tom Jones.

[3] In 1977 he was cast as Jobab in Franco Zeffirelli's TV series Jesus of Nazareth, also dubbing the main character, portrayed by Robert Powell, in the Italian version.

[4] He became a successful voice-over artist, having regularly dubbed over the voices of Jack Nicholson, James Caan, Richard Dreyfuss, Omar Sharif and Franco Nero, also dubbing Michael Douglas (a role which he shared with Oreste Rizzini) in a select number of his films.

[5] He was the Italian voice of the title character in Disney's animated film Robin Hood, Julius Caesar in Asterix the Gaul and a sportscaster in one of Goofy's shorts, Tennis Racquet.

[6] In 1999, he performed alongside Maggie Smith, Cher and Judi Dench in Tea with Mussolini, portraying Dino Grandi, and kept acting in cinema until the 2010s, when he decided to focus his career on literature.