Robert Downey Jr.

as Dr. John Dolittle

Harry Collett

as Tommy Stubbins

Michael Sheen

as Dr. Blair Müdfly

Jim Broadbent

as Lord Thomas Badgley

Antonio Banderas

as King Rassouli

Jessie Buckley

as Queen Victoria

Emma Thompson

as Poly (voice)

Rami Malek

as Chee-Chee (voice)

John Cena

as Yoshi (voice)

Kumail Nanjiani

as Plimpton (voice)

Craig Robinson

as Kevin (voice)

Ralph Fiennes

as Barry (voice)

Tom Holland

as Jip (voice)

Octavia Spencer

as Dab-Dab (voice)

Selena Gomez

as Betsy (voice)

Marion Cotillard

as Tutu (voice)

Kasia Smutniak

as Lily Dolittle

Carmel Laniado

as Lady Rose

Frances de la Tour

as Dragon (voice)

Jason Mantzoukas

as James the Dragonfly (voice)

Ralph Ineson

as Arnall Stubbins

Joanna Page

as Bethan Stubbins

Sonny Ashbourne Serkis

as Arnall Stubbins Jr.

Oliver Chris

as Sir Gareth

Clive Francis

as Archbishop

Paul Holowaty

as Navy Man

Elliot Barnes-Worrell

as Captain William Derrick

Mark Umbers

as Lieutenant

David Sheinkopf

as Don Carpenterino

Sid Sagar

as Jeff the Prisoner

Martin Pemberton

as Postman

Tim Treloar

as Humphrey the Whale (voice)

Jim Carretta

as Beard Mouse and Leona (voice)

Nick Fisher

as Mini the Sugar Glider (voice)

Matt King

as Clyde

Ranjani Brow

as Mouse (voice)

Kelly Stables

as Mouse (voice)

Scott Menville

as Army Ant (voice)

Gia Davis

as Baby Animal (voice)

Henry Holcomb

as Baby Animal (voice)

Kyrie McAlpin

as Baby Animal (voice)

Isley Zamora

as Baby Animal (voice)

Stewart Scudamore

as Pirate

Samson Kayo

as Pirate

John-Luke Roberts

as Pirate / Animal Performer

Joseph Balderrama

as Prisoner

Daniel Hoffmann-Gill

as Prisoner

Jane Leaney

as Animal Performer

Josh Jefferies

as On Set Chee-Chee / Animal Performer

Shaun McKee

as On Set Yoshi / Animal Performer

Richard Soames

as Animal Performer

Will Arnett

as Rabbit (voice) (uncredited)