Plagiotremus flavus is a species of combtooth blenny found in Fiji and Tonga in the western central Pacific Ocean. It is found at depths of up to 27m (89feet) and is associated with reefs. This species attacks other fish to feed on their mucus and scales. In Fiji, P. flavus is a Batesian mimic of Meiacanthus oualanensis, while in Tonga, it mimics Meiacanthus tongaensis.