Beginning in April 2018, Oh began a leading role in Phoebe Waller-Bridge's BBC America spy thriller series Killing Eve, portraying British intelligence agent Eve Polastri whose quarry is psychopathic assassin Villanelle played by Jodie Comer, with the women developing a mutual fascination. When she initially read the series script, Oh didn't realize she was being considered for a lead, saying she had been "brainwashed" by years of being cast as the leads' best friends. The widely praised series (having received a 100% rating on Rotten Tomatoes as of May 2018) had already been renewed for a second season before its premiere. Jenna Scherer described Oh in Rolling Stone as "a compulsively watchable actor – expressive and complex, blending wry wit and deep pathos". When Vulture declared Oh the best actress currently on television, critic Matt Zoller Seitz wrote that "It's a tour de force performance, yet so self-effacing and invisible in its effects that you come away thinking that you've seen a crackling yarn with compelling characters rather than a cultural landmark. This is a magic trick of a high order. " In 2018 Oh became the first Asian actress nominated for the Best Actress in a Drama Emmy, for that role.