Stephen Gaghan Director, Screenwriter Robert Downey Jr. Dr. John Dolittle Actor, Executive Producer Antonio Banderas King Rassouli Actor Michael Sheen Dr. Blair Müdfly Actor Jim Broadbent Lord Thomas Badgley Actor Jessie Buckley Queen Victoria Actor Harry Collett Tommy Stubbins Actor Emma Thompson Poly Voice Rami Malek Chee-Chee Voice John Cena Yoshi Voice Kumail Nanjiani Plimpton Voice Octavia Spencer Dab-Dab Voice Tom Holland Jip Voice Craig Robinson Kevin Voice Ralph Fiennes Barry Voice Selena Gomez Betsy Voice Marion Cotillard Tutu Voice Kasia Smutniak Lily Dolittle Actor Carmel Laniado Lady Rose Actor Frances de la Tour Dragon Voice Jason Mantzoukas James the Dragonfly Voice Ralph Ineson Arnall Stubbins Actor Joanna Page Bethan Stubbins Actor Dan Gregor Screenwriter Doug Mand Screenwriter Sarah Bradshaw Executive Producer Zachary Roth Executive Producer Joe Roth Producer Jeff Kirschenbaum Producer Susan Downey Producer Jonathan Liebesman Executive Producer Guillermo Navarro Cinematographer Craig Alpert Film Editing Chris Lebenzon Film Editing Danny Elfman Original Music Dominic Watkins Production Design Matthew Gray Supervising Art Direction Tom Whitehead Art Director Tom Weaving Art Director Will Coubrough Art Director Peter Dorme Art Director Alex Smith Art Director Lee Sandales Set Decoration Jenny Beavan Costume Design Lucy Bevan Casting