Jim Carrey
Horton (voice)
Cast (54)
Steve Carell
Mayor (voice)
Carol Burnett
Kangaroo (voice)
Will Arnett
Vlad (voice)
Seth Rogen
Morton (voice)
Dan Fogler
Councilman / Yummo Wickersham (voice)
Isla Fisher
Dr. Mary Lou Larue (voice)
Jonah Hill
Tommy (voice)
Amy Poehler
Sally O'Malley (voice)
Jaime Pressly
Mrs. Quilligan (voice)
Charles Osgood
Narrator (voice)
Josh Flitter
Rudy (voice)
Niecy Nash-Betts
Miss Yelp (voice)
Jesse McCartney
JoJo (voice)
Shelby Adamowsky
Hedy / Hooly (voice)
Jack Angel
Old Time Who (voice)
Caitlin Rose Anderson
Helen (voice)
Emily Anderson
Heather (voice)
Jan Rabson
Town Cryer (voice)
John Cygan
Who (voice)
Jess Harnell
Another Who (voice)
Debi Derryberry
Who Mom (voice)
Samantha Droke
Hildy / Holly (voice)
Karen Disher
Who Kid (voice)
Marshall Efron
Wickersham Guard 1 (voice)
Bill Farmer
Willie Bear (voice)
Jason Fricchione
Joe (voice)
Heather Goldenhersh
Who Girl (voice)
Selena Gomez
Helga (voice)
Jimmy Hayward
Obnoxious Who (voice)
Joey King
Katie (voice)
Christina Martino
Heidi / Haley (voice)
Ellie Martino
Hanna (voice)
Laraine Newman
Glummox Mom (voice)
Tim Nordquist
Wickersham Guard 2 (voice)
Colleen O'Shaughnessey
Angela (voice)
Laura Ortiz
Jessica (voice)
Joe Pasquale
The Dentist (voice)
Connor Anderson
Who Child #1 (voice)
Isabella Acres
Additional Voices (voice)
Bob Bergen
Additional Voices (voice)
Jeff Biancalana
Additional Voices (voice)
Madison Davenport
Additional Voices (voice)
Teresa Ganzel
Additional Voices (voice)
Kathy Graves Toon
Additional Voice (voice)
Sherry Lynn
Additional Voices (voice)
Danny Mann
Additional Voices (voice)
Mona Marshall
Additional Voices (voice)
Mickie McGowan
Additional Voices (voice)
Madison Pettis
Additional Voices (voice)
Grace Rolek
Additional Voices (voice)
Jennessa Rose
Additional Voices (voice)
Ariel Winter
Additional Voices (voice)
Fletcher Sheridan
Jojo (singing voice) (uncredited)
Crew (54)
Tim Nordquist
Editor
John Powell
Original Music Composer
Ken Daurio
Screenplay
Steve Martino
Director
Bob Gordon
Producer
Cinco Paul
Screenplay
Audrey Geisel
Executive Producer
Chris Meledandri
Executive Producer
Jimmy Hayward
Director
Bruce Anderson
Producer
Chris Wedge
Executive Producer
Paul Downs
Animation
Ricardo Curtis
Head of Story
Arun Ram-Mohan
Lighting Artist
Jeannine Berger
Post Production Supervisor
Barry E. Jackson
Visual Development
Christian Kaplan
Casting
William H. Frake III
Storyboard Artist
Martin Fuller
Storyboard Artist
Edmund Fong
Additional Storyboarding
David Esneault
Lighting Director
Chris Renaud
Storyboard Artist
Tony Maki
Storyboard Artist
Cal Brunker
Storyboard Artist
Frank Marino
Additional Storyboarding
Eric Favela
Storyboard Artist
Rich Moore
Additional Storyboarding
Crystal Chesney
Additional Storyboarding
Rafael Zentil
Storyboard Artist
Wilbert Plijnaar
Additional Storyboarding
Jony Chandra
Storyboard Artist
Karen Disher
Storyboard Artist
Stephanie Arnett
Additional Storyboarding
Jeff Biancalana
Storyboard Artist
Jeff Siergey
Additional Storyboarding
Chris Gilligan
Additional Storyboarding
Dr. Seuss
Book
Tansal Arnas
Schedule Coordinator
J.G. Quintel
Additional Storyboarding
Moroni Taylor
Storyboard Artist
Guillermo Willie Real
Set Designer
Dennis Leonard
Supervising Sound Editor
Michael Knapp
Set Designer
Kyle Macnaughton
Set Designer
Jake Parker
Set Designer
Nash Dunnigan
Set Designer
Thomas Cardone
Art Direction
Lizette Vega
Set Designer
Jamie Kirschenbaum
Senior Visual Effects Supervisor
Tom Carlson
Supervising Music Editor
Randy Thom
Sound Designer
Alen Lai
Senior Visual Effects Supervisor
Randy Thom
Supervising Sound Editor
Rhett Collier
Senior Visual Effects Supervisor