- Adrian Rawlins - Nikolai Fomin
- Alan Williams - KGB Chairman Charkov
- David Dencik - Mikhail Gorbachev
- Mark Lewis Jones - General Pikalov
- Ralph Ineson - General Tarakanov
- Barry Keoghan - Pavel
- Alex Ferns - Glukhov
- Fares Fares - Bacho
- Michael McElhatton - Prosecutor Andrei Stepashin
- Sam Strike - Misha
- Sammy Hayman - Titenok
- Matas Dirgincius - Vladimir Tishchura
- Caolan Byrne - Day Shift Worker
- Alex Blake - Petrovich
- Matthew Needham - Dmitri
- Rosie Sheehy - Nurse Pripyat
- Tomas Žaibus - Soldier (Hospital)
- Ron Cook - Old Maternity Doctor
- Peter Guinness - Major Burov
- Laurence Spellman - Commission Heli Pilot
- Alison Pargeter - BCP HQ Aide Female
- Victor McGuire - Garanin
- Sakalas Uždavinys - Ilya Ivanovich Chulkov
- Aidas Jurgaitis - Soldier (Shelter)
- Aiste S. Gram - Bartender in Polyissa Hotel
- Daniel Crossley - Stasiuk
- Lucy Russell - Marina Gruzinskaya
- Donald Sumpter - Zharkov
- Diarmaid Murtagh - Zukauskas
- Natasha Radski - Russian News Reader
- Joe Tucker - Plant Employee
- Caoilfhionn Dunne - Yenina
- Philip Barantini - Bezpalov
- Oscar Dyekjær Giese - Baranov
- Baltasar Breki Samper - Ananenko
- Pandora Colin - Dr. Vetrova
- Gerard Kearns - Pravik
- Povilas Jatkevičius - Kibenok
- Rachel Atkins - Niyazova
- Darius Petkevičius - Local Husband
- James Cosmo - Miner
- Arnas Danusas - Soldier (Miner's Bus)
- Michael Colgan - Mikhail Shadov
- James Kermack - Miner
- Karolis Vilkas - Miner
- June Watson - Old Woman Babushka
- Amanda Drew - Kremlin Aide Female
- Josef Altin - Soldier
- Sergejus Ivanovas - Survey Soldier
- Alexej Manvelov - Garo
- Josef Davies - Janek
- Velta Žygurė - Elderly Librarian
- Paulius Cizinauskas - KGB Agent Library
- Mark Bagnall - Jughashvili (Robot Operator)
- Ian Pirie - Site Officer Masha
- Andrew Sheridan - Biorobot
- Lukas Malinauskas - Biorobot Soldier
- Marius Karolis Gotbergas - Biorobot Soldier
- Michael Socha - Mikhail
- Jamie Sives - Sitnikov
- Douggie McMeekin - Yuvchenko
- Simonas Dovidauskas - KGB Driver
- Hilton McRae - Judge Milan Kadnikov
- Kieran O'Brien - Khodemchuck
- Cait Davis - Local Wife at Bar
- Michael Shaeffer - Blond Man
- Šarūnas Datenis - Soldier (Reactor Site)
- Karl Davies - Viktor Proskuryakov
- Adam Lundgren - Brazhnik
- Billy Postlethwaite - Boris Stolyarchuk
- Jay Simpson - Perevozchenko
- Ross Armstrong - Nikolai Gorbachenko
- Paulius Markevičius - Aleksandr Kudryavstev
- Karolis Kasperavičius - Viktor Degtaryenko
- Deividas Breivė - Soldier (Mobile Office)
- Brett Thomas
- Chris Roufs
- Craig Mazin
- Robert Sterne
- Martin Ware
- Jane Featherstone
- Nicola Morrow
- Chris Fry
- Julius Karvelis
- Philip Clements
- Michael Maroussas
- Anna Wright
- Stefan Henrix
- Evyen Klean
- Harry Barnes
Jamie Sives interpreta a Sitnikov en la serie.
James Cosmo hace el papel de Miner.
Kieran O'Brien hace el papel de Khodemchuck.
Victor McGuire interpreta a Garanin en la serie.
Jared Harris interpreta a Valery Legasov en la serie.
Stellan Skarsgård interpreta a Boris Shcherbina en la serie.
Emily Watson hace el papel de Ulana Khomyuk.
Paul Ritter interpreta a Anatoly Dyatlov en la serie.
Jessie Buckley hace el papel de Lyudmilla Ignatenko.
Adam Nagaitis interpreta a Vasily Ignatenko en la serie.
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