The stomach contents of 50 Cortez damselfish Stegastes rectifraenum captured at Los Frailes, Baja California Sur, Mexico were analysed to describe their diet. According to our results, S. rectifraenum is an omnivorous species with a preference for certain prey; invertebrates (benthic copepods) and algae (Bryopsis spp. and Ectocarpus spp.). Other animal components (Cerithium spp. and Olivella spp.) can also be found in their diet. No differences were observed between genders (analysis of similarity (ANOSIM), R = 0.002, P = 0.001) or among seasons (ANOSIM, R = 0.046, P = 0.001), therefore their food can be available all year at the rocky reef at Los Frailes.