Owen Wilson as John Beckwith

Vince Vaughn as Jeremy Grey

Christopher Walken as Secretary William 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 Zachary '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 Garthe

Diora Baird as Vivian

Kathryn Joosten as Chazz's Mom

Naureen Zaim as Hindu Woman

Norma Michaels as Old Irish Woman

James Carville as Himself (uncredited)

Will Ferrell as Chazz Reinhold (uncredited)

John McCain as Himself (uncredited)

Lindsay Schoneweis as Woman in Hat (uncredited)

Kelsey Wedeen as Bridesmaid (uncredited)

Rachel Sterling as Brunette

Camille Anderson as Camille

Ivana Bozilovic as Ivana

Tanaya Nicole as Woman at Jewish Reception

Brian T. Lynch as Funeral Mourner