Vegetation composition and structural diversity are important for biodiversity conservation and forest carbon storage.. Less attention has been paid to tropical forest vegetation characteristics and the carbon stock across different pools in Nigeria. This study presents the results of a rapid assessment and exploratory estimate of the woody species composition, biomass and carbon stock of six plots in order to gain quantitative insight into the carbon pools in the lowland forests across Southwest (SW) Nigeria. Using plot level quadrat (25 × 25 m) approach, this study explores the structural characteristic and carbon stock potential of the tropical natural forest. . Woody species composition, density, girth-size, height, basal area, and carbon stock from five major pools and their impact on total carbon storage were determined. A total of 89 woody species with mean density of 770.67/ha were enumerated and species structural composition, biomass and carbon stock differed among the investigated plots. Plots III and IV had the highest total number of species and woody density. The species diversity also varies across the plots, and ranged between 2.01 in Plot VI to 2.91 in Plot III. Although majority of the species present in Plots I, II, IV, and VI have lower species importance value index and smaller girth sizes, there were still few individuals with high girth-size. Above and below ground pools suggest that the study area has the capacity of storing between 145.17 to 745.57 Mg C ha− 1 of carbon. Carbon stock estimate of the aboveground pool (1,593.89 MgC/ha) was higher than the belowground pool (595.19 MgC/ha) and carbon contribution from litter (0.0203 MgC/ha) and herb (0.0067 MgC/ha) was quite low. Overall, these findings have shown that despite the ongoing anthropogenic disturbance, SW Nigeria tropical forest has considerable potential carbon sequestration.