Cillian Murphy (J. Robert Oppenheimer), Emily Blunt (Kitty Oppenheimer), Matt Damon (Leslie Groves), Robert Downey Jr. (Lewis Strauss), Florence Pugh (Jean Tatlock), Josh Hartnett (Ernest Lawrence), Casey Affleck (Boris Pash), Rami Malek (David Hill), Kenneth Branagh (Niels Bohr), Jason Clarke (Roger Robb), Scott Grimes (Rechtsbeistand), Tony Goldwyn (Gordon Gray), Macon Blair (Lloyd Garrison), James D'Arcy (Patrick Blackett), Harry Groener (Senator McGee), Gregory Jbara (Chairman Magnuson), Ted King (Senator Bartlett), Tim Dekay (Senator Pastore), Steven Houska (Senator Scott), Alden Ehrenreich (Senatsassistent), Kurt Koehler (Thomas Morgan)
