The distribution and abundance of thirteen species of regular sea urchin were assessed on Sosoikula and Nukubuco reefs, Fiji. Their morphology and behavior were contrasted relative to wave activity, water depth, substratum composition, food, and predation through all the reefs zones. Densities and relative densities of species in each zone were determined and their significance tested relative to the species distribution. Results indicated species associations with different reef areas, thus habitat preferences, which reflected species’ competitive abilities and resource partitioning. Echinometra mathaei was the most prolific and adaptable species, having the greatest densities in all zones. Peak mean densities occurred in the mid back reef area on the echinoderm flat (2.64 ind. m–2), comprising 93.6% of all echinoids found. Diadema savignyi and Diadema setosum were found at maximum densities in the boulder zone, utilizing the narrow elevated crevice space. Both these species of Diadema showed an increase in test diameters and spine lengths from the reef crest to the hard coral bommies, proportional to the increase in observed crevice size. Echinothrix diadema and Echinothrix calamaris (brown color morph) demonstrated a similar trend, but with continued growth-related migration to the Porites and soft coral zone. The white color morph of E. calamaris showed no apparent association between size distribution and crevice space. This was due to behavioral adaptations, where both juveniles and adults aggregated together in the few very large crevices found. Algal and seagrass species distributions appeared to have only a moderate influence on echinoid species distributions, as most species diets appeared broad within habitat. Predation pressure was assessed to be relatively low, with greatest predator densities on the fore reef (0.24 ind. m–2). Refuge quality and availability, moderated by predation, combined with different echinoid morphologies and behaviors, determined species distributions through the reefs varied habitats.