 | Emile Hirsch als Christopher McCandless / Alexander Supertramp |
 | Marcia Gay Harden als Billie McCandless |
 | William Hurt als Walt McCandless |
 | Jena Malone als Carine McCandless / Additional Narration (voice) |
 | Brian H. Dierker als Rainey |
 | Catherine Keener als Jan Burres |
 | Vince Vaughn als Wayne Westerberg |
 | Kristen Stewart als Tracy Tatro |
 | Hal Holbrook als Ronald "Ron" Franz |
 | Thure Lindhardt als Mads |
 | Signe Egholm Olsen als Sonja |
 | Jim Gallien als Jim Gallien |
| James J. O'Neill als Graduation Reader |
| Malinda McCollum als Waitress |
| Paul Knauls als Building Manager |
 | Zach Galifianakis als Kevin |
| Craig Mutsch als Wayne's Crew #1 |
| Jim Beidler als Wayne's Crew #2 |
| John Decker als Hutterite #1 |
| John Hofer als Hutterite #2 |
| Jerry Hofer als Hutterite #3 |
| Terry Waldner als Hutterite #4 |
| Robin Mathews als Gail Borah |
| Candice Campos als Bar Girl |
 | Steven Wiig als Lee's Ferry Ranger |
| Floyd Wall als Man In Phone Booth |
| Bryce Walters als Christopher McCandless (age 4) |
| Jim Davis als Immigration Officer |
 | Cheryl Francis Harrington als Social Worker |
 | R. D. Call als Bull |
 | Haley Ramm als Carine McCandless (age 11) |
 | Merritt Wever als Lori |
| Everett 'Insane Wayne' Smith als Insane Cain |
 | John Jabaley als Announcer |
 | Leonard Knight als Leonard Knight |
| Matt Contreras als Book Shopper #1 |
| Denise Sitton als Book Shopper #2 |
| Sharon Olds als Additional Narration (voice) |
| Carine McCandless als Additional Narration (voice) |
 | J. Nathan Simmons als Tourist (uncredited) |
| Parris Mosteller als Young Boy (voice) (uncredited) |
| Timothy Levine als Atlanta Braves fan (uncredited) |
 | Haley Sweet als Bank Teller (uncredited) |
| Aaron Wayne Hill als Big Wheel Boy (uncredited) |
 | Bart the Bear II als Bear |
| Sean Penn | Screenplay |
| Éric Gautier | Director of Photography |
| Eddie Vedder | Music |
| Kaki King | Music |
| Mary Claire Hannan | Costume Design |
| Sean Penn | Director |
| Jay Cassidy | Editor |
| Michael Brook | Original Music Composer |
| Derek R. Hill | Production Design |
| Domenic Silvestri | Art Direction |
| Francine Maisler | Casting |
| Chuck Zlotnick | Still Photographer |
| Michael Minkler | Sound Re-Recording Mixer |
| Danielle Berman | Set Decoration |
| Martín Hernández | Supervising Sound Editor |
| David Franco | Music Supervisor |
| Jacqueline Aronson | Costume Supervisor |
| Lora Hirschberg | Sound Re-Recording Mixer |
| Christopher Neely | Set Decoration |
| Martín Hernández | Sound Designer |
| Kathy Driscoll-Mohler | Casting Associate |
| Arturo Zarate | Sound Effects Editor |
| Lauren Grey | Casting Associate |
| John Richardson | Art Direction |
| Jacques Jouffret | Steadicam Operator |
| Christopher Barnett | Sound Effects Editor |
| Robin Mathews | Makeup Department Head |
| Sterfon Demings | Hair Department Head |
| Luca Kouimelis | Script Supervisor |
| Lyn Matsuda Norton | Script Supervisor |
| John J. Kelly | Executive Producer |
| Frank Hildebrand | Executive Producer |
| David Webb | Assistant Director |
| David Blocker | Executive Producer |
| Donald Frazee | Special Effects Supervisor |
| Brinton Bryan | Second Unit |
| Chris Regan | Color Timer |
| John R. Saunders | Assistant Director |
| Rod Park | Visual Effects Producer |
| Haley Sweet | Production Supervisor |
| Doug Seus | Stunt Coordinator |
| Jack Nicholson | Thanks |
| Jonathan Bell | Thanks |
| Mychael Bates | Property Master |
| Jon Krakauer | Book |
| Nerses Gezalyan | Sound Mixer |
| Tricia Pifer | Visual Effects Producer |
| Amy Fegely | Set Costumer |
| Critter Pierce | Set Costumer |
| Mike Smithson | Makeup Artist |
| Edward Tise | Sound Mixer |
| Eddie Vedder | Songs |
| Bill Pohlad | Producer |
| Sean Penn | Producer |
| Art Linson | Producer |
| Jon Krakauer | Thanks |
| Carine McCandless | Thanks |
| Walt McCandless | Thanks |
| Billie McCandless | Thanks |
| Gary Archer | Prosthetics |
| Cole S. McKay | Stunts |
| Gary J. Wayton | Stunts |
