 Orson WellesJoseph Balsamo aka Count Cagliostro | Joseph Balsamo aka Count Cagliostro |
 Nancy GuildMarie Antoinette / Lorenza | Marie Antoinette / Lorenza |
 Akim TamiroffGitano | Gitano |
 Frank LatimoreGilbert de Rezel | Gilbert de Rezel |
 Valentina CorteseZoraida | Zoraida |
 Margot GrahameMme. du Barry | Mme. du Barry |
 Stephen BekassyViscount de Montagne | Viscount de Montagne |
 Berry KroegerAlexandre Dumas, Sr. | Alexandre Dumas, Sr. |
 Gregory GayeChambord / Monk (as Gregory Gay) | Chambord / Monk (as Gregory Gay) |
 Raymond BurrAlexandre Dumas, Jr. | Alexandre Dumas, Jr. |
| CCharles GoldnerDr. Franz Anton Mesmer | Dr. Franz Anton Mesmer |
| LLee KreselKing Louis XVI / Innkeeper | King Louis XVI / Innkeeper |
 Robert AtkinsKing Louis XV | King Louis XV |
| NNicholas BruceDe Remy | De Remy |
| FFranco CorsaroChico | Chico |
| AAnnielo MeleJoseph Balsamo as a Child | Joseph Balsamo as a Child |
 Ronald AdamCourt President | Court President |
 Bruce BelfrageCrown Prosecutor | Crown Prosecutor |
| AAlexander DanaroffDr. Duval / Baron von Minden | Dr. Duval / Baron von Minden |
 Leonardo ScavinoGaston / Beniamino Balsamo (as Leon Lenoir) | Gaston / Beniamino Balsamo (as Leon Lenoir) |
 Tamara ShayneMaria Balsamo | Maria Balsamo |
| JJoop van HulzenMinister of Justice | Minister of Justice |
| PPeter TrentDr. Mesmer's Friend | Dr. Mesmer's Friend |
| GGiuseppe VarniBoehmer | Boehmer |
 Tatyana PavlovaGrieving Mother | Grieving Mother |
 Harriet Medin(uncredited) | (uncredited) |
| VValentino Bruchi(uncredited) | (uncredited) |
 Ludmilla Dudarova(uncredited) | (uncredited) |
 Rosina Galli(uncredited) | (uncredited) |
 Silvana Mangano(uncredited) | (uncredited) |
