He has acted in over 150 Bollywood films and over 25 Bhojpuri films. In most of the films that he has acted, he played a pivotal role, contributing to the flow of the storyline. In 1960, he made his acting debut with the Hindi film Honeymoon. He did several thrillers and most notable among them were Ek Saal Pehla and Lal Bangla. He is remembered widely for his team up with megastar Rajesh Khanna. Along with Aradhna, they have worked together in several hit films like Haathi Mere Saathi, Mehbooba, Ittefaq, Amar Prem, Aakhir Kyon, Avtaar, Roti, Aan Milo Sajna and Mere Jeevan Saathi. He was good friends with Rakesh Roshan and Jeetendra. Apart from playing villainous roles, he has also played several spy roles.
Sujit Kumar is remembered as the first superstar of Bhojpuri films. His notable Bhojpuri films include Bidesiya, Champa Chameli, Sampurna Teerth yatra, Dangal Loha Singh and Mai Ke Lal just to name a few. He played best friend roles of lead Actors, Policeman roles, Spy roles and Negative roles.
Apart from Acting he has directed and produced several films. He made his production debut with the 1986 film Anubhav. Among the famous films that he has produced are Manisha Koirala and Sunny Deol starrer Champion and Rishi Kapoor, Arbaaz Khan and Juhi Chawla starrer Daraar.
Apart from films he has also acted in the famous horror series on television Zee Horror Show.