He won two Olivier Awards, both at the National Theatre, in 2008 for his portrayal of Sir Fopling Flutter in The Man of Mode, and for playing the William Shakespeare villain Iago in Othello in 2014.
He played Bill Tanner in four James Bond films: Quantum of Solace (2008), Skyfall (2012), Spectre (2015), and No Time to Die (2021); and in various video games of the franchise.
Television roles include Michael Callow in the debut episode of the anthology Black Mirror, The National Anthem (2011), Michael Baker in the sitcom Count Arthur Strong (2013–2017), Lord Lucan in the two-part thriller Lucan (2013), the Creature in the horror drama Penny Dreadful (2014–2016), and Stephen in the dystopian mini-series Years and Years (2019).
[9] Kinnear performed in Phyllida Lloyd's production of Mary Stuart, and in Trevor Nunn's Hamlet, in which he played Laertes.
[15] From September 2013, the Bush Theatre in London staged Kinnear's debut play The Herd, directed by Howard Davies.
[8] For The Threepenny Opera (a "play with songs") at the Olivier Theatre from May to October 2016, Kinnear found his "dormant" singing voice for the role of Macheath.
[21] Kinnear portrays Bill Tanner in the Daniel Craig–era James Bond film series after taking over from Michael Kitchen.
In 2014, he played the fictional character, Detective Nock, in The Imitation Game based loosely on the biography Alan Turing:The Enigma by Andrew Hodges.
[26] He appeared in the lead role of Prime Minister Michael Callow in "The National Anthem", the first episode of the anthology series Black Mirror.
[25] In 2021, Kinnear played Neo-Nazi Colin Jordan in the television drama Ridley Road[33] and was Edward Williams in the BBC's The Mezzotint.
[34] In 2023 he played the fictional character of British Prime Minister Nicol Trowbridge in the Netflix series The Diplomat alongside Keri Russell.
In 2010, he played Flugkapitän Jürgen Rahl in the BBC Radio drama Slipstream as a disaffected German pilot who joins a mission to steal an alien spacecraft harboured by the Nazis.