Narrator / Horton / Dr. H. Hoovey (voice)
Hans Conried
Jane Kangaroo / Mother Who / Baby Who / Cindy Lou Who (voice)
June Foray
Junior Kangaroo / Various Whos / Quizmo McKwoff / JoJo (voice)
Chuck Jones
Wickersham Brother (voice) (uncredited)
Thurl Ravenscroft
Animation
Phil Roman
Director
Ben Washam
Producer
Teleplay
Dr. Seuss
Irven Spence
Background Designer
Philip DeGuard
Irv Wyner
Carl Bell
Tom Ray
Angel Esparza
Music
Eugene Poddany
Richard Thompson
Production Design
Maurice Noble
Hal Ambro
George Nicholas
Layout Supervisor
Don Morgan
Graphic Designer
Don Foster