| Name | Character | Episodes |
|---|---|---|
| John Carson | Narrator | 7 |
| David Suchet | Edward Teller | 7 |
| Sam Waterston | Robert Oppenheimer | 7 |
| Edward Hardwicke | Enrico Fermi | 7 |
| Shane Rimmer | Ed Condon | 7 |
| Alexander Knox | Henry Stimson | 7 |
| Garrick Hagon | Frank Oppenheimer | 7 |
| James Maxwell | Lloyd Garrison | 7 |
| Barry Dennen | Isidor Rabi | 7 |
| David Baxt | Colonel John Lansdale | 7 |
| Phil Brown | Lewis Strauss | 7 |
| Jana Shelden | Kitty Oppenheimer | 7 |
| Matthew Guinness | Hans Bethe | 7 |
| Milton Johns | George Kistiakowsky | 7 |
| Peter Banks | Joseph Volpe | 7 |
| Bob Sherman | Ernest Lawrence | 7 |