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

Tamara Hickey

Marilyn Richards

Tom O'Brien

Neighbor's Husband

Paul Pape

Dick Drayne (voice)

Chris Edgerly

Edmund Dinis (voice)

Wally Wingert

Newscaster (voice)

Piotr Michael

Newscaster (voice)