<Ul> <Li> Eli Marienthal as Hogarth Hughes, an intelligent, energetic and curious 9 - year - old boy with an active imagination . Marienthal's performances were videotaped and given to animators to work with, which helped develop expressions and acting for the character . </Li> <Li> Vin Diesel as The Iron Giant, a fifty - foot, metal - eating robot . Created for an unknown purpose, the Giant involuntarily reacts defensively if he recognizes anything as a weapon, immediately attempting to destroy it . The Giant's voice was originally to be electronically modulated but the filmmakers decided they "needed a deep, resonant and expressive voice to start with," so they hired Vin Diesel . </Li> <Li> Christopher McDonald as Kent Mansley, a government agent sent to investigate sightings of the Iron Giant . The logo on his official government car says he is from the "Bureau of Unexplained Phenomena". </Li> <Li> Harry Connick, Jr. as Dean McCoppin, a beatnik artist and junkyard owner . Bird felt it appropriate to make the character a member of the beat generation, as they were viewed as mildly threatening to small - town values during that time . An outsider himself, he is among the first to recognize the Giant as no threat . </Li> <Li> Jennifer Aniston as Annie Hughes, the widow of a military pilot and Hogarth's mother . </Li> <Li> John Mahoney as General Shannon Rogard, an experienced and levelheaded military leader in Washington, D.C. who strongly dislikes Mansley . </Li> <Li> M. Emmet Walsh as Earl Stutz, a sailor and the first man to see the robot . </Li> <Li> James Gammon as Marv Loach, a foreman who follows the robot's trail after it destroys the power station . <Ul> <Li> James Gammon also voices Floyd Toubeaux </Li> </Ul> </Li> <Li> Cloris Leachman as Mrs. Karen Tensedge, Hogarth's schoolteacher </Li> <Li> Ollie Johnston and Frank Thomas as the train engineers . Johnston and Thomas were animators and members of Disney's Nine Old Men . Bird cited them as inspirations for his career and incorporated their voices and likenesses into the film . </Li> </Ul> <Li> Eli Marienthal as Hogarth Hughes, an intelligent, energetic and curious 9 - year - old boy with an active imagination . Marienthal's performances were videotaped and given to animators to work with, which helped develop expressions and acting for the character . </Li> <Li> Vin Diesel as The Iron Giant, a fifty - foot, metal - eating robot . Created for an unknown purpose, the Giant involuntarily reacts defensively if he recognizes anything as a weapon, immediately attempting to destroy it . The Giant's voice was originally to be electronically modulated but the filmmakers decided they "needed a deep, resonant and expressive voice to start with," so they hired Vin Diesel . </Li> <Li> Christopher McDonald as Kent Mansley, a government agent sent to investigate sightings of the Iron Giant . The logo on his official government car says he is from the "Bureau of Unexplained Phenomena". </Li>

Who does vin diesel play in the iron giant