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

Victor Warren

Stephen Smith

David De Beck

Sargent Shriver

Matthew Lawler

Dun Gifford

Thomas Kee

Walter Steele

Andria Blackman

Joan Kennedy

Tim Jackson

Joseph Kopechne

Damien Di Paola

Ray LaRosa

Gary Tanguay

TV Interviewer

Tony Viveiros

Floor Producer

Tamara Hickey

Marilyn Richards

Nancy O'Brien

Neighbor

Tom O'Brien

Neighbor's Husband

Michele Proude

Vicki

Michael Fennimore

Chief of Staff

Dustin Tucker

Senatorial Aide

Paul Pape

Dick Drayne (voice)

Chris Edgerly

Edmund Dinis (voice)

Wally Wingert

Newscaster (voice)

Piotr Michael

Newscaster (voice)

Bill Mootos

Older Reporter

Philip Dorn Hebert

Jack Crimmins

Patrick Sheehan

Lawyer

Michael Swanson

Security Agent

Susan Garfield

Senate Staffer (uncredited)

Paul Bellefeuille

Dike House Resident (uncredited)

Joe Cali

Reporter (uncredited)

William Galatis

Shiretown Inn Guest (uncredited)

Bill Porter

Investigative News Reporter (uncredited)

Sigrid Lium

Senate Staffer (uncredited)