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