Owen Wilson as John Beckwith

Vince Vaughn as Jeremy Grey

Christopher Walken as Secretary Cleary

Rachel McAdams as Claire Cleary

Isla Fisher as Gloria Cleary

Jane Seymour as Kathleen Cleary

Ellen Albertini Dow as Grandma Mary Cleary

Keir O'Donnell as Todd Cleary

Bradley Cooper as Sack Lodge

Ron Canada as Randolph

Henry Gibson as Father O'Neil

Dwight Yoakam as Mr. Kroeger

Rebecca De Mornay as Mrs. Kroeger

David Conrad as Trap

Jennifer Alden as Christina Cleary

Geoff Stults as Craig

James McDonnell as Attorney

Jesse Henecke as Attorney

Lou Cutell as Old Jewish Man

Sparkle as Old Jewish Woman

Frank Ray Perilli as Old Italian Man

Patricia Place as Old Italian Woman

Chao-Li Chi as Old Chinese Man

Norma Michaels as Old Irish Woman

Noel De Souza as Old Indian Man

Ivana Bozilovic as Ivana

Camille Anderson as Camille

Rachel Sterling as Brunette

Diora Baird as Vivian

Ned Schmidtke as Frank Meyers

Jennifer Massey as Woman

Dylan James Turner as Bratty Kid

Sophia Blouin as Flower Girl

Stephen J. Downs as Franklin

Larry Joe Campbell as Best Man

Mark Duane Anderson as Secret Service Agent

Irene Roseen as Elderly Woman

Jules Mandel as Rabbi

Betsy Ames as Betty

Carson Elrod as Flip

Joshua Wheeler as Kip

John G. Pavelec as Ken

Charles Kahlenberg as Priest

Kathryn Joosten as Chazz's Mom

Karen Miller as Chazz's Girlfriend

Tanaya Nicole as Woman at Jewish Reception

Naureen Zaim as Hindu Woman

Cindy Taylor as Girl at Irish Wedding

Melanie Hawkins as Girl Who Cries

Summer Altice as Girl Who Cries

Lisa Beach as Wedding Planner

Lovelynn Vanderhorst as Wedding Planner

Phyllis Samhaber as Woman at Table

O.J. Watson as Man at Table

Al Cerullo as Helicopter Pilot

Will Ferrell as Chazz Reinhold (uncredited)

James Carville as James Carville (uncredited)

John McCain as John McCain (uncredited)

Lindsay Schoneweis as Woman in Hat (uncredited)

Kelsey Wedeen as Bridesmaid (uncredited)

Brian T. Lynch as Funeral Mourner (uncredited)

Joe Koons as Irish Waiter (uncredited)