Karthika was born to former Indian actress Radha, and is the niece of actress Ambika. She has two siblings, a brother and a sister, Thulasi Nair, who is also a South Indian actress. She did her schooling in Podar International School in Mumbai and is now studying an international degree in Business from college affiliated to London School of Economics.
She made her debut at a very early age of 17 in the 2009 Telugu film, Josh opposite Naga Chaitanya. Her second movie was in Tamil called Ko pairing with Jiiva which did very well at the box office. She then appeared in the Malayalam film, Makaramanju directed by Lenin Rajeendran, starring alongside ace cinematographer and director Santosh Sivan. She have done a Wonderfull acting in Annakodi.