布莱恩·丹内利
Brian.Dennehy
饰：Gen. Leslie Groves
大卫·斯特雷泽恩
David Strathairn
饰：J. Robert Oppenheimer
迈克尔·塔克
Michael Tucker
饰：Leo Szilard
休姆·克罗宁
Hume Cronyn
饰：James F. Byrnes
Richard A. Dysart
Richard A. Dysart
饰：President Harry S. Truman
哈尔·霍尔布鲁克
Hal Holbrook
饰：Gen. George Marshall
巴纳德·休斯
Barnard Hughes
饰：Secretary of War Henry Stimson
约翰·麦克马丁
John McMartin
饰：Dr. Arthur Compton
大卫·奥根·斯提尔斯
David Ogden Stiers
饰：President Franklin D. Roosevelt
Anne Twomey
饰：Kitty Oppenheimer
劳伦斯·戴恩
Lawrence Dane
朗·弗雷泽
Ron Frazier
饰：Colonel Pash
欧勒克·克鲁帕
Olek Krupa
饰：Edward Teller
伯尼·麦克伦尼
Bernie McInerney
Ken Pogue
Ken Pogue
饰：Groves's Commanding Officer
加里·莱因克
Gary Reineke
饰：Dwight D. Eisenhower
阿兰·斯卡费
Alan Scarfe
约翰·塞茨
John Seitz
饰：演员 Actor/Actress
托尼·夏尔赫布
Tony Shalhoub
饰：Enrico Fermi
朗·怀特
Ron White
饰：Colonel Nichols
Peter Boretski
饰：Albert Einstein
帕特里克·布林
Patrick Breen
饰：Richard Feynman
瓦拉斯塔·瓦拉纳
Vlasta Vrana
饰：Hans Bethe
George Popovich
饰：Samuel Goudsmit
Lorne Brass
Lorne Brass
饰：Klaus Fuchs
迈克尔·西奈尔尼科夫
Michael Sinelnikoff
饰：Lord Rutherford
Graham Haley
Graham Haley
饰：Haakon Chevalier
Kliment Denchev
饰：Michael Polanyi
蒂莫西·韦伯
Timothy Webber
饰：Colonel Lansdale
哈里·斯坦德乔夫斯基
Harry Standjofski
饰：Robert Wilson
Lia Sargent
Lia Sargent
饰：Mrs. Wisnovsky
David Gow
David Gow
饰：Jack Wisnovsky
Michael Farrell
Michael Farrell
饰：Shapp
Isabelle Mejias
饰：Mrs. Trowbridge
乔治
George R. Robertson
饰：Ed Condon
Dee McCafferty
饰：William 'Deke' Parsons
汤姆·巴特勒
Tom Butler
饰：Captain DeSilva
Robert Morelli
Robert Morelli
饰：T.O. Jones
David Bolt
David Bolt
饰：Harry Gold
大卫·费里
David Ferry
饰：Army Major
Heinar Pillar
饰：Fleischmann (as Heinar Piller)
François Klanfer
饰：Haagen Kistiakowski
Joel Miller
饰：George Kistiakowski
迈克尔·J·雷诺兹
Michael J. Reynolds
饰：Kenneth Bainbridge
Ed McGibbon
饰：Admiral William D. Leahy
Nicholas Kilbertus
Nicholas Kilbertus
饰：Paul Tibbets (as Nick Kilbertus)
Joe Cazalet
饰：Air Force Guard
斯科特·汤姆森
Scott Thomson
饰：Chemist
Bob Clout
饰：Alfred MacCormack
Terrence Labrosse
Terrence Labrosse
饰：Allan Dulles
Philip Spensley
饰：British Sr. Officer
Frederick Neumann
饰：Alexander Sachs
Norris Domingue
饰：General Pa Watson
Steve Barry
饰：Los Alamo Scientist (uncredited)
亚瑟·霍尔顿
Arthur Holden
饰：Scientist (uncredited)
约翰·皮尔迈尔
John Pielmeier
饰：Seth
Ester Spitz
饰：Trude Weiss
Stephan Balint
饰：Eugen Wigner
Fritz Buchinger
Fritz Buchinger
饰：Dr. Vincent
Diana Fajrajsl
Diana Fajrajsl
饰：Ilse Polanyi
Jonathan Wise
Jonathan Wise
饰：Robert Serber
Jon Baggaley
饰：James Tuck
Roland Hewgill
饰：Army General
Stan Gibbons
Stan Gibbons
饰：John J. McCloy
Delise Alison
Delise Alison
饰：London Pedestrian
Alex Guard
Alex Guard
饰：British Jr. Officer
理查德·戴萨特
Richard Dysart
饰：President Harry S. Truman