Plastic waste has been identified in otariid excreta around the world. However, in Peru, previous reports of these contaminants in O. byronia have not been evaluated. In this study, we report the presence and shapes of microplastics (MPs) found in scat samples of this species, collected within a natural protected area in southern Peru. A total of 47 plastic particles classified as fibers and fragments were identified, whose average length was 3.02 and 1.19, respectively. The origin of these millimetric plastic particles in O. byronia scats is unknown; however, other studies have associated the incidence of MPs to the diet of the animals. For future studies, we suggest improving the detection techniques of MPs to continue research efforts on contaminants in free ranging aquatic species.