In 2006, Kunal made his feature film debut opposite the critically acclaimed actress Tabu in M.F. Hussain’s semi-autobiographical film Meenaxi: A Tale of Three Cities. The movie bombed at the box office but the soundtrack composed by the Mozart of Madras, A. R. Rahman was well received. After this unconventional film, Kunal appeared in the runaway hit Rang De Basanti, which over the years has received a cult status in both Indian and international cinema. Starring an ensemble cast comprising Aamir Khan, Siddharth Narayan, Soha Ali Khan, Kunal Kapoor, R. Madhavan, Sharman Joshi, Atul Kulkarni and British actress Alice Patten, the movie opened to an overwhelmingly positive critical and commercial response. For his portrayal of Aslam Khan, Kunal received his first Filmfare nomination in the category of Best Supporting Actor.
Post Rang De Basanti, the actor signed a three-film deal with Yash Raj films, and went on to feature in films like Laaga Chunari Mai Daag, Aaja Nachle, and Bachna Ae Haseeno, under the banner. Except Bachna Ae Haseeno, which starred Ranbir Kapoor, and Deepika Padukone in the lead role, the other two films bombed at the box office. In 2011, he appeared in Farhan Akhtar’s blockbuster Don 2 and in 2012, he starred in the critically well-received film Luv Shuv Tey Chicken Khurana.
His 2016 release includes the Indian drama film, Dear Zindagi. Directed by Gauri Shinde, the movie stars Alia Bhatt, Shah Rukh Khan, Aditya Roy Kapur, Kunal Kapoor, and Angad Bedi in pivotal roles.