Horton słyszy Ktosia

Amy Poehler

Sally O'Malley (voice)

Ariel Winter

Additional Voices (voice)

Bill Farmer

Willie Bear (voice)

Bob Bergen

Additional Voices (voice)

Carol Burnett

Kangaroo (voice)

Charles Osgood

Narrator (voice)

Colleen O'Shaughnessey

Angela (voice)

Dan Fogler

Councilman / Yummo Wickersham (voice)

Danny Mann

Additional Voices (voice)

Debi Derryberry

Who Mom (voice)

Fletcher Sheridan

Jojo (singing voice) (uncredited)

Grace Rolek

Additional Voices (voice)

Heather Goldenhersh

Who Girl (voice)

Isabella Acres

Additional Voices (voice)

Isla Fisher

Dr. Mary Lou Larue (voice)

Jack Angel

Old Time Who (voice)

Jaime Pressly

Mrs. Quilligan (voice)

Jan Rabson

Town Cryer (voice)

Jason Fricchione

Joe (voice)

Jess Harnell

Another Who (voice)

Jesse McCartney

JoJo (voice)

Jim Carrey

Horton (voice)

Jimmy Hayward

Obnoxious Who (voice)

Joe Pasquale

The Dentist (voice)

Joey King

Katie (voice)

John Cygan

Who (voice)

Jonah Hill

Tommy (voice)

Josh Flitter

Rudy (voice)

Karen Disher

Who Kid (voice)

Laraine Newman

Glummox Mom (voice)

Laura Ortiz

Jessica (voice)

Madison Davenport

Additional Voices (voice)

Madison Pettis

Additional Voices (voice)

Marshall Efron

Wickersham Guard 1 (voice)

Mickie McGowan

Additional Voices (voice)

Mona Marshall

Additional Voices (voice)

Niecy Nash

Miss Yelp (voice)

Samantha Droke

Hildy / Holly (voice)

Selena Gomez

Helga (voice)

Seth Rogen

Morton (voice)

Sherry Lynn

Additional Voices (voice)

Steve Carell

Mayor (voice)

Teresa Ganzel

Additional Voices (voice)

Tim Nordquist

Wickersham Guard 2 (voice)

Will Arnett

Vlad (voice)