Tree diameter distributions play an important role in stand performance. Diameter distribution model was developed for Sakponba Forest Reserve. Systematic sampling technique was adopted. A total of 613 trees were measured in 96 sample plots. Diameter at breast height (dbh) at 1.3m above ground data were measured for tree species with dbh ≥ 10cm in the confines of the sampling units. Data collected were analysed using probability density function (pdf), then ranked based on Kolmogorov smirnov. The best six distributions [Log-Logistic (3p), Burr, Dagum, Gen-Logistic, Gen Extreme value and Log normal] were used for fitting the diameter data. The results indicated that the trees in the lower diameter class were more in number than the upper diameter class. Log-Logistic distribution was adjudged more flexible when tested with Kolmogorov smirnov The reason is because the calculated value [Log-Logistic (3P) = 0.04477] was the lowest value and smaller than the tabulated values (D = 0.05 at p ≥ 0.05). This implied that the data followed the specified distribution and that Log-Logistic (3P) can appropriately provide a better fit for the diameter data in Sakponba Forest Reserve.