Jason Clarke

Ted Kennedy

Kate Mara

Mary Jo Kopechne

Ed Helms

Joseph Gargan

Bruce Dern

Joseph Kennedy

Jim Gaffigan

Paul Markham

Olivia Thirlby

Rachel Schiff

Clancy Brown

Robert McNamara

Taylor Nichols

Ted Sorensen

John Fiore

Chief Arena

Lexie Roth

Nance Lyons

Victor Warren

Stephen Smith

David De Beck

Sargent Shriver

Matthew Lawler

Dun Gifford

Andria Blackman

Joan Kennedy

Tamara Hickey

Marilyn Richards

Nancy O'Brien

Neighbor

Bob Jaffe

Reporter #2

Paul Pape

Dick Drayne (voice)

Chris Edgerly

Edmund Dinis (voice)

Wally Wingert

Newscaster (voice)

Piotr Michael

Newscaster (voice)

Bill Mootos

Older Reporter

William Galatis

Shiretown Inn Guest (uncredited)