| Benedict Cumberbatch | Sherlock Holmes |
| Martin Freeman | Dr. John Watson |
| Una Stubbs | Mrs. Hudson |
| Rupert Graves | DI Lestrade |
| Mark Gatiss | Mycroft Holmes |
| Louise Brealey | Molly Hooper |
| Amanda Abbington | Mary Watson |
| Lindsay Duncan | Lady Smallwood |
| Simon Kunz | Sir Edwin |
| Sacha Dhawan | Ajay |
| Marcia Warren | Vivian |
| Eleanor Matsuura | DI Hopkins |
| Paul Chequer | DI Dimmock |
| Gabrielle Glaister | Ambassador |
| Harry Gostelow | Husband |
| Charles Edwards | David Welsborough |
| Amanda Root | Emma Welsborough |
| Rob Callender | Charlie Welsborough |
| Sian Brooke | Elizabeth
(as Siân Brooke) |
| Richard Syms | Vicar |
| Neal Barry | Ray Kingsley |
| Edward Judge | Craig |
| Andrew Bone | Jack Sandeford |
| Albert Magashi | Karim |
| Tanya Moodie | Ella |
| Daniel Hoffmann-Gill | Gold Teeth Man |
| James Holmes | Plane Passenger |
| Eiry Thomas | Stewardess |
| Aleksandar Mikic | Guard |
| David Colbourn | Male Client |
| Hattie Ladbury | Female Client |
| David Cromarty | Terrorist
(uncredited) |
| Hassan Khan | MI6 Officer
(uncredited) |
| Pino Maiello | Hostage
(uncredited) |
| Lars Mikkelsen | Charles Magnussen
(archive footage) (uncredited) |
| Francesco Rochira | Gunman
(uncredited) |
| Matthew Rohman | Tortured Soldier
(uncredited) |
| Andrew Scott | Jim Moriarty
(archive footage) (uncredited) |