Eastman was born in Genoa, Italy, and studied at the Centro Sperimentale di Cinematografia in Rome and at the Drama School held of Alessandro Fersen. He took his Americanized alias "George Eastman" when he was cast as a "heavy" in many Spaghetti Westerns made in the late 1960s and early 1970s. In 1972 he played the villain in The Call of the Wild which starred Charlton Heston and was directed by Ken Annakin.
Eastman later became a regular performer in many movies directed by Joe D'Amato, for whom he also wrote many screenplays. Their first work together was Cormack of the Mounties (aka Giubbe rosse) in 1975.
He was a very familiar face in Italian B-cinema in the early 1980s, being generally cast as a villain, thanks to his towering 6'9" height, and his dark and menacing looks. He co-starred in many Italian science fiction films such as Bronx Warriors, The New Barbarians, Endgame, Ironmaster, 2020 Texas Gladiators and After the Fall of New York. His most famous movie is the gory horror film Anthropophagous, directed by Joe D'Amato in 1980, in which he played the monster. He also starred in D'Amato's Erotic Nights of the Living Dead, Porno Holocaust and Absurd (aka Anthropophagous 2).
Two of his greatest major villain roles were in Rabid Dogs (aka Kidnapped, 1974) and Blastfighter (1984). He appeared in Paramount's 1985 biblical film King David playing Goliath in David's childhood flashback scene. In 1986, he performed as Stefano in the movie Regalo di Natale, directed by Pupi Avati. He also wrote and directed the science fiction film Metamorphosis/ DNA Formula Letale (produced by Joe D'Amato) in 1990, after which he quit acting to concentrate on his screenwriting. He is now a well regarded author in Italian television and only acts occasionally. (In 2003, he returned to acting in La rivincita di Natale, a film directed by Pupi Avati.)
