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