He made his feature film debut in 1998, co-starring with Jamie Lee Curtis in Halloween H20: 20 Years Later for Miramax. Hartnett gained fame for his role as Cpt Danny Walker in Pearl Harbor, and has starred since then for a variety of well-known directors such as Ridley Scott, Brian De Palma, Robert Rodriguez, Tran Anh Hung, Roland Joffé and Michael Bay. Now in love with the stage, he went on to star in a slew of high school plays. He became a vegetarian at the age of 12 but ate meat during the shooting of The Black Dahlia for his role as a boxer. Although the series was cancelled after sixteen episodes, Hartnett had made a name for himself. He was originally set to play the role of Tino in Deuces Wild, but dropped out to star in Pearl Harbor. in the early 2000s, Hartnett was approached several times to play the role of Clark Kent/Superman in the upcoming film(at the time helmed by Brett Ratner), but always turned it down, not wanting to commit to a predicted ten-year role.