 | Rod Steiger als The Intermediary |
 | Adolfo Celi als Msgr. Radini Tedeschi |
 | Giorgo Fortunato als Segretario del Nunzio Roncalli |
| Ottone Candiani als Il Prete Peccatore di Venezia |
| Alfonso Orlando als Il Parrroco |
 | Alberto Rossi als Angelo Roncalli - Age 7 |
| Giovanni Rossi als Angelo Roncalli - Age 10 |
| Fabrisio Rossi als Angelo Roncalli - Age 4 |
 | Pietro Germi als Pontiff's Father |
| Rita Bertocchi als Pontiff's Mother |
| Antonio Bertocchi als Uncle Xavier |
| Antonio Ruttigni als Don Pietro, Parrocco di Carviso |
 | Pope John XXIII als Self (archive footage) (uncredited) |
| Ennio Michettoni | Set Decoration |
| Venanzio Biraschi | Sound Engineer |
| Harry Saltzman | Producer |
| Idelmo Simonelli | Camera Operator |
| Ermanno Olmi | Director |
| Carla Colombo | Editor |
| Gaspare Palumbo | Production Manager |
| Pope John XXIII | Novel |
| Piero Portalupi | Director of Photography |
| Ennio Michettoni | Production Design |
| Ermanno Olmi | Screenplay |
| Vincenzo Labella | Screenplay |
| Vincenzo Labella | Producer |
| Franco Potenza | Original Music Composer |
| Antonietta Gianesin | Production Secretary |
| Mimmola Girosi | Assistant Director |
| Cesare Fontana | Assistant Camera |
| Jolanda Adamo | Assistant Editor |
| Giuseppe Baghdighian | Additional Editing |
| Franco Potenza | Conductor |
