| Episode credited cast: |
 | Will Rosser | - | Narrator (voice) |
 | Anthony Summers | - | Himself - Author of 'The Secret Life of J. Edgar Hoover' |
 | John Fox | - | Himself - FBI Historian |
 | William Gallinaro | - | Himself - Crime Detective |
 | Athan Theoharis | - | Himself - Author of 'The FBI and American Democracy' |
 | Curt Gentry | - | Himself - Author of 'J. Edgar Hoover: The Man and the Secrets' |
 | John M. Dowd | - | Himself - US Justice Department (as John Dowd) |
 | William Turner | - | Himself - Former FBI Agent (as Bill Turner) |
 | Bill Bonanno | - | Himself - Son of Mafia Boss Joseph Bonanno |
| Rest of cast listed alphabetically: |
 | Inga Arvad | - | Herself, Danish journalist (archive footage) |
 | Milton Berle | - | Himself (archive footage) |
 | Joseph Bonanno | - | Himself, mobster (archive footage) |
 | Judy Cerda | - | Louisa Stewart |
 | Frank Costello | - | Himself, mobster (archive footage) |
 | John Dillinger | - | Himself (archive footage) |