Emile Hirsch was born in Topanga, California, the son of Margaret, a visual artist and teacher who designed pop-up books, and David Hirsch, an industrial consultant, manager, and producer. His older sister Jenny introduced him to acting. Hirsch was raised in Los Angeles, California, and Santa Fe, New Mexico, where he lived with his mother after his parents divorced. He attended Paul Revere Middle School and the Academy of Music at Alexander Hamilton High School in Los Angeles.

Hirsch began acting at the age of eight, appearing in minor roles on television shows and made-for-television films, including Kindred: the Embraced; Sabrina, the Teenage Witch and NYPD Blue. He made his film debut with the 2002 drama, The Dangerous Lives of Altar Boys, where he starred opposite Kieran Culkinin the story of two Catholic school boys. His next role was in the prep school drama, The Emperor's Club, which was released later in 2002. Both films received generally positive reviews, but performed only moderately at the box office.

Hirsch was subsequently cast opposite Elisha Cuthbertin the 2004 teen comedy, The Girl Next Door, and as a result gained renown among teenage audiences. The Mudge Boy, an independent film that he had starred in before making Girl Next Door, was given a limited release in the summer of 2004. Hirsch next appeared in Imaginary Heroes, a drama about a dysfunctional family, which received a limited release in February 2005 but failed to reach a wider audience, despite mostly positive reviews.

In 2005, Hirsch starred in Lords of Dogtown; the film, about a number of well-known skaters of the 1970s, was released on June 3, 2005, but ultimately performed poorly at the box office. He subsequently appeared in Alpha Dog, a dark drama starring Bruce Willisand Sharon Stonein which he played a character based on real-life drug dealer Jesse James Hollywood.

Hirsch next played adventurer Christopher McCandless in Sean Penn's critically acclaimed adventure-drama Into the Wild, released on September 21, 2007. He lost 40 pounds for the role and was noted in reviews as a potential Academy Award nominee for the film, also receiving a Screen Actors Guild nomination for best actor.