Cillian MurphyJ. Robert Oppenheimer
Emily BluntKitty Oppenheimer
Matt DamonLeslie Groves
Robert Downey Jr.Lewis Strauss
Florence PughJean Tatlock
Josh HartnettErnest Lawrence
Casey AffleckBoris Pash
Rami MalekDavid Hill
Kenneth BranaghNiels Bohr
Benny SafdieEdward Teller
Jason ClarkeRoger Robb
Dylan ArnoldFrank Oppenheimer
Tom ContiAlbert Einstein
James D'ArcyPatrick Blackett
David DastmalchianWilliam Borden
Dane DeHaanKenneth Nichols
Alden EhrenreichSenate Aide
Tony GoldwynGordon Gray
Jefferson HallHaakon Chevalier
David KrumholtzIsidor Rabi
Matthew ModineVannevar Bush
Scott GrimesCounsel
Kurt KoehlerThomas Morgan
John GowansWard Evans
Macon BlairLloyd Garrison
Harry GroenerSenator McGee
Gregory JbaraChairman Magnuson
Ted KingSenator Bartlett
Tim DeKaySenator Pastore
Steven HouskaSenator Scott
Petrie WillinkDutch Student
Matthias SchweighöferWerner Heisenberg
Alex WolffLuis Alvarez
Josh ZuckermanRossi Lomanitz
Rory KeaneHartland Snyder
Michael AngaranoRobert Serber
Emma DumontJackie Oppenheimer
Sadie StrattonMary Washburn
Britt KyleBarbara Chevalier
Guy BurnetGeorge Eltenton
Tom JenkinsRichard Tolman
Louise LombardRuth Tolman
Michael Andrew BakerJoe Volpe
Jeff HephnerCongressman
Olli HaaskiviEdward Condon
David RysdahlDonald Hornig
Josh PeckKenneth Bainbridge
Jack QuaidRichard Feynman
Brett DelBuonoConcerned Scientist
Gustaf SkarsgårdHans Bethe
James UrbaniakKurt Gödel
Trond Fausa AurvågGeorge Kistiakowsky
Devon BostickSeth Neddermeyer
Danny DeferrariEnrico Fermi
Christopher DenhamKlaus Fuchs
Jessica Erin MartinCharlotte Serber
Ronald AugusteJ. Ernest Wilkins
Máté HaumannLeo Szilard
Olivia ThirlbyLilli Hornig
Jack Cutmore-ScottLyall Johnson
Harrison GilbertsonPhilip Morrison
James RemarHenry Stimson
Will RobertsGeorge C. Marshall
Pat SkipperJames Byrnes
Steve CoulterJames Conant
Jeremy John WellsAAF Officer
Sean AveryWeatherman
Adam KroegerArmy Captain
Drew KenneySoldier
Bryce JohnsonAAF Officer 2
Flora NolanBurn Victim
Kerry WestcottLaughing Woman
Christina HogueKissing Woman
Clay BunkerKissing Man
Tyler BeardsleyWeeping Man
Maria Teresa ZuppettaConsoling Woman
Kate FrenchPresidential Aide
Gary OldmanHarry Truman
Hap LawrenceLyndon Johnson
Meg SchimelpfenigSenator's Assistant (uncredited)