He attended Daly College, a boarding school in Indore, enrolled at R. D. National College in Bandra, Mumbai, and later joined the Film and Television Institute of India (FTII) in Pune. He was known as "Dipak Dar" in Film and Television Institute of India among his friends. As a young boy, the film industry was drawn to him, partly because of his father's association with it.  Kumar starred in Do Boond Pani in 1971 and went on to play the lead roles in several more movies. Kumar saw his career suffer with the release of movies like Jangal Mein Mangal, among others; however, despite this "slump", Kumar started to work in Gujarati movies, where he quickly attained a cult following, and the title "The Bachhan of Gujarati Cinema. Rakesh Roshan's Khudgarz got him back to Hindi cinema, in which negative roles in films like Tezaab and Khuda Gawah won him accolades as an antihero.