Paul Terry as James Henry Trotter

Miriam Margolyes as Aunt Sponge / Glowworm (voice)

Joanna Lumley as Aunt Spiker

Pete Postlethwaite as The Magic Man

Simon Callow as Grasshopper (voice)

Richard Dreyfuss as Centipede (voice)

Jane Leeves as Ladybug (voice)

Susan Sarandon as Miss Spider (voice)

David Thewlis as Earthworm (voice)

Steven Culp as James' Father

Susan Turner-Cray as James' Mother

Cirocco Dunlap as Girl with Telescope

Kathryn Howell as Woman in Bathrobe

Mike Starr as Cop

Michael Girardin as Reporter #1

J. Stephen Coyle as Reporter #2

Tony Haney as Reporter #3

Mario Yedidia as Street Kid

Jeff Mosley as Hard Hat Man

Jeff Bennett as Centipede (singing voice) (uncredited)

Sally Stevens as Glowworm (singing voice) (uncredited)