David Cross
Ian
Anna Faris
Jeanette (voice)
Matthew Gray Gu
Simon (voice)
Jason Lee
Dave
Justin Long
Alvin (voice)
Christina Applegate
Brittany (voice)
Alan Tudyk
Simone (voice)
Ross Bagdasarian, Jr.
Alvin (singing voice) (uncredited)
Janice Karman
Theodore / The Chipettes (singing voice) (uncredited)
Jesse McCartney
Theodore (voice)
Amy Poehler
Eleanor (voice)
Chad Krowchuk
Waiter
Luisa d'Oliveira
Tessa
Phyllis Smith
Flight Attendant
Andy Buckley
Captain Correlli
Lauren Gottlieb
Club Woman #2
Jenny Slate
Zoe
Tucker Albrizzi
Tucker / Kite Kid
Nelson Wong
Casino Guy
Michael P. Northey
Hawaiian Shirt Guy
Ian Harmon
Monster
Sophia Aguiar
Club Woman #1
Jeremy Palko
Cruise Guy (uncredited)
Steve Vining
Simon (singing voice) (uncredited)