Naagulu (Chiranjeevi) is forced to consume poison since childhood by his father making him immune to the snake bit. Every full moon day, he kills women and on one such day, he kills the woman he loves. Her brother Raju (Narasimharaju) gets suspicious and starts his investigation only to make a shocking discovery. Punnami Naagu is a remake of the Kannada film Hunnimeya Rathriyalli.