Emile Hirsch as Christopher McCandless / Alexander Supertramp

Marcia Gay Harden as Billie McCandless

William Hurt as Walt McCandless

Jena Malone as Carine McCandless / Additional Narration (voice)

Brian H. Dierker as Rainey

Catherine Keener as Jan Burres

Vince Vaughn as Wayne Westerberg

Kristen Stewart as Tracy Tatro

Hal Holbrook as Ronald "Ron" Franz

Thure Lindhardt as Mads

Signe Egholm Olsen as Sonja

Jim Gallien as Jim Gallien

James J. O'Neill as Graduation Reader

Malinda McCollum as Waitress

Paul Knauls as Building Manager

Zach Galifianakis as Kevin

Craig Mutsch as Wayne's Crew #1

Jim Beidler as Wayne's Crew #2

John Decker as Hutterite #1

John Hofer as Hutterite #2

Jerry Hofer as Hutterite #3

Terry Waldner as Hutterite #4

Robin Mathews as Gail Borah

Candice Campos as Bar Girl

Steven Wiig as Lee's Ferry Ranger

Floyd Wall as Man In Phone Booth

Bryce Walters as Christopher McCandless (age 4)

Jim Davis as Immigration Officer

Cheryl Francis Harrington as Social Worker

R. D. Call as Bull

Haley Ramm as Carine McCandless (age 11)

Merritt Wever as Lori

Everett 'Insane Wayne' Smith as Insane Cain

John Jabaley as Announcer

Leonard Knight as Leonard Knight

Matt Contreras as Book Shopper #1

Denise Sitton as Book Shopper #2

Sharon Olds as Additional Narration (voice)

Carine McCandless as Additional Narration (voice)

J. Nathan Simmons as Tourist (uncredited)

Parris Mosteller as Young Boy (voice) (uncredited)

Timothy Levine as Atlanta Braves fan (uncredited)

Haley Sweet as Bank Teller (uncredited)

Aaron Wayne Hill as Big Wheel Boy (uncredited)

Bart the Bear II as Bear