Tinker Tailor Soldier Spy received critical acclaim. Rotten Tomatoes reports an approval rating of 83% based on 228 reviews, with an average rating of 7.79/10. The site's critics' consensus states: "Tinker Tailor Soldier Spy is a dense puzzle of anxiety, paranoia, and espionage that director Tomas Alfredson pieces together with utmost skill."[23] Metacritic, which assigns a normalised rating in the 0–100 range based on reviews from top mainstream critics, calculated an average score of 85 based on 42 reviews, indicating "universal acclaim".[24]

Jonathan Romney of The Independent wrote, "The script is a brilliant feat of condensation and restructuring: writers Peter Straughan and the late Bridget O'Connor realise the novel is overtly about information and its flow, and reshape its daunting complexity to highlight that".[25] David Gritten of The Daily Telegraph declared the film "a triumph" and gave it a five star rating,[26] as did his colleague, Sukhdev Sandhu.[27] Stateside, Peter Travers of Rolling Stone wrote, "As Alfredson directs the expert script by Peter Straughan and Bridget O'Connor, the film emerges as a tale of loneliness and desperation among men who can never disclose their secret hearts, even to themselves. It's easily one of the year's best films."[28] M. Enois Duarte of High-Def Digest also praised the film as a "brilliant display of drama, mystery and suspense, one which regards its audience with intelligence".[29]

The Telegraph's Guy Stagg, meanwhile, thought that the movie needed a car chase in the middle.[30] Writing in The Atlantic, le Carré admirer James Parker favourably contrasted Smiley with the James Bond franchise but found this Tinker Tailor adaptation "problematic" compared to the 1979 BBC mini-series. He wrote: "To strip down or minimalize le Carré, however, is to sacrifice the almost Tolkienesque grain and depth of his created world: the decades-long backstory, the lingo, the arcana, the liturgical repetitions of names and functions".[31]

Keith Uhlich of Time Out New York named Tinker Tailor Soldier Spy the fourth-best film of 2011, calling it "a visually stunning adaptation with a stellar cast."[32] In 2020, Uhlich named it the ninth-best film of the 2010s.[33]