Jason Segel as Peter Bretter

Kristen Bell as Sarah Marshall

Mila Kunis as Rachel Jansen

Russell Brand as Aldous Snow

Bill Hader as Brian Bretter

Jonah Hill as Matthew Van Der Wyk

Liz Cackowski as Liz Bretter

Jack McBrayer as Darald

Maria Thayer as Wyoma

Paul Rudd as Chuck

Jason Bateman as Animal Instincts Detective

William Baldwin as Detective Hunter Rush

Kristen Wiig as Yoga Instructor

Da'Vone McDonald as Dwayne

Steve Landesberg as Dr. Rosenbaum

Kalani Robb as Helpful Hawaiian Waiter

Murray Miller as Photographer

Taylor Wily as Kemo

Kala Alexander as Greg

Francesca Delbanco as Hostess at Buffet

Branscombe Richmond as Keoki

Billy Bush as Billy Bush (Himself)

Peter Gray Lewis as Suspect on Animal Instincts

Trula M. Marcus as Lawyer on Crime Scene

Kirk Fox as Mixer

June Diane Raphael as Ann

Ahna O'Reilly as Leslie

Tanisha Harper as Model

Carla Gallo as Gag Me Girl

Cynthia Lamontagne as Female Bartender

Max Alexander as Big Dracula Head

Carla Alapont as Spanish Sex Girl

Michael Oosterom as Puppeteer

Peter Salett as Keyboard Player

Jesse Heiman as Theater Audience Member (uncredited)

Gedde Watanabe as Hotel Manager