Sen started his career, assisting auteur Bimal Roy at New Theatres in Kolkata, however Kolkata based film industry was now on the decline, thus Roy shifted base to Bombay (now Mumbai) along with his team in 1950, which included Sen, Hrishikesh Mukherjee, Nabendu Ghosh, Kamal Bose and later Salil Chaudhury, and by 1952 he has restarted the second phase of his career with Maa (1952) for Bombay Talkies. Though he had made Assamese film, Biplabi (1948), after his shift, he made his Hindi film debut with Parivaar (1956), produced by Bimal Roy and starring Kishore Kumar, and Usha Kiran, however he continued working in Bengali cinema. He assisted Roy in Parineeta (1953) and Biraj Bahu (1954). Next he made Bengali film, Chalachal in 1956 starring Arundhati Devi, which was a success, many years later he remade the film in Hindi as Safar, which was also a hit.