In the early 1970s during the Cold War, the head of British Intelligence, Control, resigns after an operation in Budapest, Hungary goes badly wrong. It transpires that Control believed one of four senior figures in the service was in fact a Russian agent - a mole - and the Hungary operation was an attempt to identify which of them it was. Smiley had been forced into retirement by the departure of Control, but is asked by a senior government figure to investigate a story told to him by a rogue agent, Ricky Tarr, that there was a mole. Smiley considers that the failure of the Hungary operation and the continuing success of Operation Witchcraft (an apparent source of significant Soviet intelligence) confirms this, and takes up the task of finding him. Through the efforts of Peter Guillam, Smiley obtains information that eventually leads him to Jim Prideaux, the agent at the heart of the Hungary fiasco...
| Alec Guinness | |
| Mark Strong | Jim Prideaux |
| Michael Jayston | |
| John Hurt | Control |
| Anthony Bate | |
| Zoltán Mucsi | Magyar |
| Péter Kálloy Molnár | Hungarian Waiter |
| George Sewell | |
| Ilona Kassai | Woman in Window |
| Bernard Hepton | |
| Imre Csuja | KGB Agent |
| Tony Pierce-Roberts | Cinematographer |
| Gary Oldman | George Smiley |
| Toby Jones | Percy Alleline |
| David Dencik | Toby Esterhase |
| Ciarán Hinds | Roy Bland |
| Colin Firth | Bill Haydon |
| Kathy Burke | Connie Sachs |
| Benedict Cumberbatch | Peter Guillam |
| Stephen Graham | Jerry Westerby |
| Arthur Nightingale | Bryant |
| Tom Hardy | Ricki Tarr |
| Simon McBurney | Oliver Lacon |
| Amanda Fairbank-Hynes | Belinda |
| Peter O'Connor | Fawn |
| Roger Lloyd-Pack | Mendel |
| Matyelok Gibbs | Mrs. Pope Graham |
| Phillip Hill-Pearson | Norman |
| Jamie Thomas King | Kaspar |
| Stuart Graham | Minister |
| Konstantin Khabenskiy | Polyakov |
| Sarah Jane Wright | Mary Alleline (as Sarah-Jane Robinson) |
| Katrina Vasilieva | Ann Smiley |
| Linda Marlowe | Mrs. McCraig |
| William Haddock | Bill Roach |
| Erksine Wylie | Spikeley |
| Philip Martin Brown | Tufty Thesinger |
| Tomasz Kowalski | Boris |
| Svetlana Khodchenkova | Irina |
| Alexandra Salafranca | Turkish Mistress |
| Denis Khoroshko | Ivan |
| Oleg Dzhabrailov | Sergei |
| Gillian Steventon | Listening Woman |
| Nick Hopper | Janitor Alwyn |
| Laura Carmichael | Sal |
| Rupert Procter | Guillam's Boyfriend |
| John le Carré | Christmas Party Guest |
| Michael Sarne | Voice of Karla (voice) |
| Christian McKay | Mackelvore |
| Jean-Claude Jay | French Man at Residency |
| Tom Stuart | Ben |
| Peter Bartfay | Hungarian Secret Agent (voice) (uncredited) |
| Alberto Iglesias | Composer |
| Sarah Linda | Miss Robinson (uncredited) |
| Hoyte Van Hoytema | Cinematographer |
| Nick Shaw | Civil Servant (uncredited) |
| Dino Jonsäter | Editor |
| Maria Djurkovic | Production Designer |
| Eva Von Mitzka | MI5 Spy (uncredited) |
| Tom Brown | Art Director |
| Zsuzsa Kismarty-Lechner | Art Director |
| Craig Narramore | Set Decorator |
| Sophie Phillips | Set Decorator |
| Simon Riley | Set Decorator |
| James M. Spencer | Set Decorator |
| Réka Belsô | key second second assistant director: Budapest |
| Sarah Stuart | Set Decorator |
| Béla Tollay | Set Decorator |
| Luisa Uribe | Set Decorator |
| Merih Ertas | second assistant director: Istanbul |
| Lloyd Vincent | Set Decorator |
| Ian Whiteford | Set Decorator |
| Greg Winter | Set Decorator |
| Anthony Szuch | Set Decorator |
| Réka Kovács | second second assistant director: Budapest |
| Safa Demirkan | Custome Designer |
| Dan Grace | Custome Designer |
| Gábor Homonnay | Custome Designer |
| Edith Kähler | Custome Designer |
| Burak Müjdeci | third assistant director: Istanbul |
| Sinéad O'Sullivan | Custome Designer |
| Nicholas Roche-Gordon | Custome Designer |
| Réka Szabó | second assistant director: Budapest |
| Edwina Sercombe | Custome Designer |
| Robert Karn | Assistant Director |
| Hilal Sezer | Custome Designer |
| Adrian Simmons | Custome Designer |
| Beril Sinan | Custome Designer |
| Katalin Ujvari | Custome Designer |
| Yagiz Alp Akaydin | first assistant director: Turkey |
| Zoltán Bonta | first assistant director: Hungary |
| James Chambers | third assistant director: second unit |
| Laura De Selincourt | crowd second assistant director |
| Mark Hopkins | second assistant director |
| Miklos Keleti | third assistant director: Hungary |
| Zoe Liang | co-second assistant director |
| Mikael Marcimain | second unit director |
| Andrew McEwan | first assistant director: second unit |
| Paul Mindel | second assistant director: second unit |
| Alex Oakley | first assistant director |
