Tropical rainforest contributes immensely to the richness, diversity and productivity of ecosystem. This study aimed to determine the structure, biodiversity and carbon stocks of Okomu protected forest in Nigeria. Simple random technique was adopted in selection of 9 compartments and in each compartment 4 plots of size was selected with 36 plots of (25 m x 25 m x 36 plots), making a total of 2.25 ha selected from the entire forest. Shannon-Wiener diversity index, Shannon's equitability of species evenness, Margalef's index of species richness and volume equations were used to determine species diversity, evenness, richness and tree structure respectively. There were 790 individual trees, 351 stems ha-1 belonging to 67 tropical hardwood species, 86 genera and 31 families. About 24% of tree species in this protected forest were among tree species that needs urgent conservation measures. The total volume was estimated to be from 1970.40 to 9437.76 m3 with an average of 4643.20 m3 ha-1, an indication of vertical and horizontal structure confirm the growing natural of this protected forest. Accumulation of total biomass was estimated to be from 1150.72 to 6795.20 kg ha-1 with an average of 2927.72 kg ha-1. The carbon stock in this protected forest was estimated to be from 575.36 to 3397.60 kg ha-1 with an average of 1463.88 kg ha-1. The forest serves as biodiversity hotspot due to high Shannon-Wiener index and evenness computed for the compartments. This serves as information for management of protected forests, with potentials for nature conservation and carbon sequestration.