The terrestrial mollusc species richness and diversity in Omo Forest Reserve, Ogun State, Nigeria, was studied using a combination of direct search and leaf-litter sieving techniques. In total, 28 species and 639 individuals in 7 molluscan families were collected from 17 plots of 400 m² each. Species richness varied from 3 to 14 (mean 8.59) and the number of individuals from 8 to 67 (mean 37.59) per plot. Species richness was dominated by the carnivorous Streptaxidae (36%) and herbivorous Subulinidae (32%), and numerical abundance by the Subulinidae (56%) and Streptaxidae (32%). The most abundant species was the large subulinid, Subulona pattalus, contributing almost 25% of the total number of individuals. Terrestrial molluscs with small populations and narrow distributional ranges are at great risk of local extinction if forest destruction continues unabated. Studies on the molluscan diversity in Omo Forest Reserve will assist in producing an inventory for biodiversity conservation management in Nigeria.