Jim Carrey

Horton (voice)

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

Miss Yelp (voice)

Jesse McCartney

JoJo (voice)

Shelby Adamowsky

Hedy / Hooly (voice)