After her studies, Kaur moved to Mumbai and worked as a print model. She began working as a theater actress appearing in plays such as Baghdad Wedding, All About Women and Red Sparrow, working with directors like Sunil Shanbag and Manav Kaul. Kaur was launched in a two-part music video for the songs "Tera Mera Pyar" by Kumar Sanu and "Yeh Kya Hua" by Shreya Ghoshal in 2004. The videos were directed by writer-editor Apurva Asrani. She also did TV advertisements. Kaur made her film debut with a small role in an English film, One Night with the King, which was shot in Rajasthan. Her Hindi film debut came with Peddlers in 2012, produced by Anurag Kashyap. The film was screened at Cannes Film Festival to good reviews. Kaur came to public attention when she appeared in a Cadbury Silk commercial. Kaur attended the Cannes festival for the second time for the romantic film The Lunchbox. The film was a commercial and critical success. Kaur received rave reviews for her portrayal of a lonely wife who begins a friendship with a man through letters. Raja Sen of Rediff.com said of Kaur's performance: "It is a disarmingly natural performance that is impossible to forget and difficult to analyse, and in this limited space one may merely express admiration." Jay Weissberg of Variety called her a "radiant presence" and Pratim D. Gupta of The Telegraph said that "Nimrat strips off all the sentimentality to attach dignity and grace to the character. This one's a sparkling debut." In 2014, Kaur appeared as ISI agent Tasneem Qureishi in the fourth season of the American TV seriesHomeland. The same year she committed to star with Rajkummar Rao in an untitled psychological drama to be directed by Saurabh Shukla. In 2016, she acted in the war drama Airlift, alongside Akshay Kumar. Based on the civil operation of evacuation of Indians based in Kuwait during the Iraq-Kuwait war, the film was released on 22 January to mostly positive reviews. Rajeev Masand in his review wrote: "For the most part, the film feels authentic, and Nimrat Kaur blends right in. Just a wee bit awkward in the early scenes, she comes into her own by the time she must deliver a scathing monologue during a crisis of faith over her husband's actions." The film was a financial success. Kaur also began portraying Rebecca Yedlin in the second season of the American television series Wayward Pines in 2016. In 2017, Kaur starred as Shikha Sharma in the Hindi web seriesThe Test Case. She returned for the eighth and final season of Homeland as a series regular in February 2020.
