Karunakaran's father is a former RAW agent and he grew up in New Delhi, before later moving to Trichy with his parents, where he met short film maker and friend Nalan Kumarasamy.He Studied his secondary schooling at Sri Akilandeswari Vidyalaya Trichy. He initially made a career as chemical engineer, graduating from SASTRA University, and then as an IT professional at Accenture, before Nalan approached him to feature in a short film he was making for the reality television show, Naalaya Iyakkunar. Karunakaran had featured in such short film ventures at school and Nalan had cast him in Nenjuku Neethi, which went on to win the first place award that season. Sundar C gave him brief roles in two of his ventures, while he made his first breakthrough portraying Vijay Sethupathi's friend in Karthik Subbaraj's Pizza (2012), after which he left work and concentrated on a career in films.
Nalan subsequently cast him in his feature film debut Soodhu Kavvum, for which Karunakaran won rave reviews. His appearance in the "Kasu Panam Thuttu" song also was well received and prompted several further offers for the actor. His performance in Yaamirukka Bayamey was appreciated by critics. The Times of India wrote, "A large part of the credit should go to Karuna, who manages to make Sharath both ambivalent and funny", while Sify wrote that he was "a scream" and The Hindu called it an "exceptional performance".He has over half-a-dozen upcoming films, including Jigarthanda, Nanbenda, Kanithan, Kappal, Mahabalipuram, Aadama Jaichomada and Aindhaam Thalaimurai Sidha Vaidhiya Sigamani.