After finishing his education at age 21, Siddharth landed the role of assistant director for Mani Ratnam's Kannathil Muthamittal. He made his debut in Telugu Film Industry with Boys, directed by Shankar. He next debuted in Bollywood as part of the critically acclaimed blockbuster Rang De Basanti which also starred Aamir Khan. Siddharth received the Star Screen Debut Award for his role as Karan Singhania in the film.