He has acted as a child artist in his father's film Vettiya Madichu Kattu. He was also an assistant director in his sister, Saranya Bhagyaraj's debut, Parijatham. He then made his acting debut in Sakkarakatti, produced by S. Thanu and directed by Kala Prabhu which ran average at the box office, the song Taxi Taxi composed by A. R. Rahman was a chartbuster. His performance received mixed reviews, Behindwoods cited : "Shanthanu has to play a thinly sketched hero, but he puts energy and charm into everything he does. He is more than promising- he’s star material, and he’ll survive this wreck", while Sify said: "Shantanoo has that star quality to him which is so rare to find these days. But he is wasted in a role in which he just romance his heroines and dances",Nowrunning said: "Shanthanoo is fairly convincing as a cool college dude who metro audiences would love. He has not much to do beyond hanging out with his friends and cuddling the two heroines. Though the young hero seems bubbly, Prabhu is not able to tap his potential".His next venture is Angel John, his debut film in malayalam in which shared screen space with Mohanlal, In this film he played a youth who fedup of life tries to commit suicide but god saves and helps him. The film did average business. His next film was Siddu +2 which was directed by his father. The film didn't do well at the box-office, his performance is somewhat well received. In 2011, his next release was Kanden which managed to do well, he had another release in 2011, Aayiram Vilakku in which he played an ordinary boy by shedding his chocolate boy image. Next he did Ammavin Kaipesi which got positive response. Currently, he is doing Amali Thumali with Nakul and Telugu film Love in Hyderabad which is a remake of his own Tamil film Siddu +2 and Vaaimai.