Horton
Jim Carrey
Mayor of Who-ville
Steve Carell
Kangaroo (voice)
Carol Burnett
Salley O'Malley
Amy Poehler
Vlad (voice)
Will Arnett
Jo Jo
Jesse McCartney
Morton (voice)
Seth Rogen
Dr. Larue
Isla Fisher
Yummo
Dan Fogler
Tommy
Jonah Hill
Mrs. Quilligan (voice)
Jaime Pressly
Charles Osgood
Rudy
Josh Flitter
Jessica
Laura Ortiz
Narrator (voice)
Charles Osgood
Miss Yelp (voice)
Niecy Nash
Katie
Joey King
Hedy / Hooly (voice)
Shelby Adamowsky
Old Time Who (voice)
Jack Angel
Caitlin Rose Anderson
Heather (voice)
Emily Anderson
Helen (voice)
Caitlin Rose Anderson
Town Cryer (voice)
Jan Rabson
Who (voice)
John Cygan
Another Who (voice)
Jess Harnell
Who Mom (voice)
Debi Derryberry
Samantha Raye Droke
Who Kid (voice)
Karen Disher
Hildy / Holly (voice)
Samantha Droke
Wickersham Guard 1 (voice)
Marshall Efron
Willie Bear (voice)
Bill Farmer
Joe (voice)
Jason Fricchione
Who Girl (voice)
Heather Goldenhersh
Helga (voice)
Selena Gomez
James Hayward
Obnoxious Who (voice)
Jimmy Hayward
Christina Martino
Glummox Mom (voice)
Laraine Newman
Heidi / Haley (voice)
Christina Martino
Wickersham Guard 2 (voice)
Tim Nordquist
Hanna (voice)
Ellie Martino
Angela (voice)
Colleen O'Shaughnessey
The Dentist (voice)
Joe Pasquale
Christoph Maria Herbst
Uwe Büschken
Who Child #1 (voice)
Connor Anderson
Anke Engelke
Additional Voices (voice)
Isabella Acres
Additional Voices (voice)
Bob Bergen
Klaus-Dieter Klebsch
Bernd Rumpf
Additional Voices (voice)
Jeff Biancalana
Lutz Schnell
Additional Voices (voice)
Madison Davenport
Victoria Sturm
Additional Voices (voice)
Teresa Ganzel
Additional Voice (voice)
Kathy Graves Toon
Additional Voices (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