Campbell Scott
Narrator (voice)
Boyd Gaines
Chairman Gray (voice)
Daniel Gerroll
Colonel Pash
Michael Stuhlbarg
Edward Teller
Ellen Katz
The Stenographer
Harold Agnew
Self
Jeremy Bernstein
Self
Freeman Dyson
Self
Richard Rhodes
Self
Martin J. Sherwin
Self
Joseph McCarthy
Self (archive footage)
J. Robert Oppenheimer
Self (archive footage/photos)
David Strathairn
J. Robert Oppenheimer
Herbert York
Self
Marvin L. Goldberger
Self
Priscilla McMillan
Self
Robert Christy
Self
Roy Glauber
Self
Harry S. Truman
Self (Archive Footage)
J. Edgar Hoover
Self (Archive Footage/Photos)
Lewis Strauss
Self (Archive Photos)
Dwight D. Eisenhower
Self (Archive Photos)
Eleanor Roosevelt
Self (Archive Footage)
Edward Teller
Self (Archive Footage/Photos)
Lyndon B. Johnson
Self (Archive Footage)
Zoë Wanamaker
Self- Narrator