The web series released on ZEE5's platform on Octoto mixed reviews. In 2020 Karthik starred in ZEE5's web series Mugilan alongside Ramya Pandian. In December 2020, however, Karthik Raj was replaced due to unforeseen reasons as quoted in the channel's official statement.
The serial made Karthik a household name.
In 2017, Karthik essayed the role of Adithyaa in the Tamil daily soap Sembaruthi alongside newcomer Shabana Shajahan. The films, however, failed in the box office and his performance received mixed reviews. He has acted as a lead actor in the movies 465 and Naalu Peruku Nalladhun Edhuvum Thappilla. He also rendered his voice as a narrator in a short film "Yaanum Neeyum" starring Vetri, his co-actor in K5. He participated in Jodi Number One Season 7 with Nancy Jennifer. Kana Kaanum Kaalangal Kalooriyin Kadhai was followed by Ram Vinayakâs Office. Karthik started his acting career with the TV show, Kana Kaanum Kaalangal Kalooriyin Kadhai (2011-2012), where he essayed the role of Karthikeyan.