 | Paolo Villaggio als Dr. Jekyll / Mr Hyde |
 | Edwige Fenech als Barbara Wimply |
 | Gianrico Tedeschi als James / Jeeves |
 | Gordon Mitchell als Pretorius |
 | Paolo Paoloni als Professor |
 | Guerrino Crivello als Student |
 | Eolo Capritti als Henchman |
 | Francesco Anniballi als Henchman |
 | Walter Williams als PANTAC Top President |
 | Clemente Ukmar als Henchman |
 | Geoffrey Copleston als Archibald Gold |
| Paola Arduini als Stewardess |
 | Angelo Boscariol als PANTAC Board Member (uncredited) |
 | Luciano Foti als Class Member (uncredited) |
 | Alfonso Giganti als Industrialist (uncredited) |
 | Juba Kennerley als Gentleman (uncredited) |
 | Giuseppe Marrocco als PANTAC Board Member (uncredited) |
 | Fulvio Mingozzi als PANTAC Board Member (uncredited) |
 | Alessandro Tedeschi als Professor introducing Jekyll (uncredited) |
 | Luciano Zanussi als PANTAC Board Member (uncredited) |
| Steno | Director |
| Piero De Bernardi | Screenplay |
| Steno | Screenplay |
| Pipolo | Idea |
| Castellano | Idea |
| Robert Louis Stevenson | Novel |
| Leonardo Benvenuti | Story |
| Leonardo Benvenuti | Screenplay |
| Piero De Bernardi | Story |
| Steno | Story |
| Giovanni Manganelli | Co-Writer |
| Massimo Tavazzi | Set Decoration |
| Marisa Crimi | Costume Design |
| Elisabetta Poccioni | Costume Design |
| Raimondo Crociani | Editor |
| Luciano Spadoni | Production Design |
| Carlo Bartolini | Production Manager |
| Ennio Guarnieri | Director of Photography |
| Sergio Salvati | Director of Photography |
| Armando Trovajoli | Original Music Composer |
| Renato Jaboni | Executive Producer |
| Giovanni Manganelli | First Assistant Director |
| Lamberto Palmieri | Unit Manager |
| Marina Mattoli | Script Supervisor |
| Lucia Nolano | Production Secretary |
| Leonardo Curreri | Administration |
| Pina Triunveri | Assistant Editor |
| Renato Ranieri | Camera Operator |
| Franco Bruni | Camera Operator |
| Massimo Iabone | Sound |
| Antonio Scaramuzza | Assistant Camera |
| Maurizio Lucchini | Assistant Camera |
| Francesco Narducci | Still Photographer |
| Gianfranco Mecacci | Makeup Artist |
| Franco Schioppa | Makeup Artist |
| Mirella Ginnoto | Hairstylist |
| Sergio Gennari | Hairstylist |
| Bruno Moreal | Sound Mixer |
| Luciano Martino | Producer |
