George Segal as Brooks Wilson

Eva Marie Saint as Selma Wilson

Sterling Hayden as Lepridon

Keenan Wynn as Edward

Nancie Phillips as Nelly

Janis Young as Grace

David Doyle as Will

Paul Sparer as Marve

Andrew Duncan as Willy

Sherry Lansing as Susan

Roland Winters as Plommie

Edgar Stehli as Mr. Kramm

Calvin Holt as Danny

Mina Kolb as Diane

Diana Douglas as Mrs. Shavelson

David Ford as Al

James Manis as Charles

Mart Hulswit as Ted

John Fink as Brad

William Duffy as Jay

Irving Selbst as Benny

Martin Harvey Friedberg as Roger

Lorraine Cullen as Lizzie

Cheryl Bucher as Hannah

Ed Crowley as Mr. Shavelson

Roy Scheider as Skip

Sab Shimono as Byron

Eileen O'Neill as Cindy

Diane Davies as Barbie

Robert Paget as Party Guest (uncredited)

John Reidy as Flower Delivery Man (uncredited)

Betsy von Furstenberg as Grace's Aunt (uncredited)