| Name | Character | Episodes |
|---|---|---|
| Michael Jayston | Quiller | 13 |
| Moray Watson | Angus Kinloch | 13 |
| Sinéad Cusack | Roz | 3 |
| Prunella Gee | Diane | 2 |
| Nigel Stock | Loman | 2 |
| John Rhys-Davies | Leindorf | 1 |
| Colin McCormack | Reporter | 1 |
| T. P. McKenna | Buchanan | 1 |
| Julian Glover | Shroder | 1 |
| Ronald Lacey | Dr. Visto | 1 |
| Keith Barron | Truscott | 1 |
| Lalla Ward | Tracy Fischer | 1 |
| Paul Maxwell | Colonel Fischer | 1 |
| George Cole | Mays | 1 |
| John Savident | Sir Ian Dalrymple | 1 |
| Donald Sumpter | Brenman | 1 |
| Ed Bishop | Frank Ilroy | 1 |
| Christopher Neame | Myers | 1 |
| Isla Blair | Germaine Allenby | 1 |
| Brian Glover | Sergeant | 1 |
| Peter Tuddenham | Dr. Erling Norgaard | 1 |
| Shane Rimmer | Harry Brent | 1 |
| Esmond Knight | General Pickford | 1 |
| Robin Sachs | Dieter | 1 |
| Edward Judd | Colonel Chimenti | 1 |
| Paul Angelis | Vickers | 1 |
| John Lee | Sir Michael Foster | 1 |
| Hans Meyer | Major Hardtmann | 1 |
| John Baskcomb | Hastings | 1 |
| Jack McKenzie | Man | 1 |
| Peter Jeffrey | Colonel Hythe | 1 |