Reef fish assemblages under fishing pressure generally exhibit a lower fish biomass, abundance, and size structure, which can be counteracted with the creation of marine protected areas (MPAs). The effectiveness of MPAs relies on enforcement and compliance, which is particularly challenging in developing countries with financial and socioeconomic limitations. By combining underwater visual surveys (UVS) and baited remote underwater video stations (BRUVS), we determined the abundance, size distribution, and biomass of economic (e.g., target and ornamental species) and ecological (e.g., small/large predators and herbivorous) indicator fish groups inside and outside a no-take MPA from the north Pacific coast of Costa Rica. The biomass of economic fish groups was not affected by protection, yet overall abundance and size distribution of fishes differed between no-take and open-fishing zones. These results suggest that although illegal fishing may be occurring inside the MPA, there are at least partial benefits of protection on particular groups within the fish assemblage. Herbivores and ornamental fishes, two groups that are targeted by the artisanal compressor fishery and by the aquarium trade, respectively, had higher biomass and were more abundant inside the no-take MPA. Additionally, large shark species (e.g., Galeocerdo cuvier , Carcharhinus leucas , C. limbatus ) were only present inside the MPA. Habitat quality was particularly important for ornamental fishes which showed higher biomass in areas with high coral cover. Our study adds to a growing body of evidence suggesting that, even with limited enforcement, MPAs still provide ecological benefits for reef fish assemblages.