Lem / Rover (voice)

Justin Long

Chuck

Dwayne Johnson

Neera

Jessica Biel

Skiff (voice)

Seann William Scott

Gen. Grawl

Gary Oldman

Professor Kipple

John Cleese

Glar

Alan Marriott

Eckle (voice)

Freddie Benedict

Soldier Vesklin (voice)

Mathew Horne

Soldier Vernkot (voice)

James Corden

Alien Mailman (voice)

Alan Cumming

Ingo Albrecht

Ripley / Rover (voice)

Frank Welker

Additional Voices (voice)

Lewis Macleod

Additional Voices / Chief Gorlock (voice) (uncredited)

Rupert Degas

Lem's Dad (voice)

Jim Cummings

Raul Richter

Additional Voices (voice)

Rebecca Front

Lem's Mom (voice)

Renée Zellweger

Teacher (voice)

Candi Milo

Additional Voices (voice)

Vincent Marzello

Andy Samberg

Udo Schenk

Additional Voices (voice)

Emma Tate

Additional Voices (voice)

Pete Atkin

Additional Voices (voice)

Laurence Bouvard

Additional Voices (voice)

Brian Bowles

Skiff

Sebastian Schulz