One Hundred And Eighty samples of True big-scale fish (Brycinus macrolepidotus Valenciennes, 1850) were collected bi-monthly from June – November, 2017, from River Ogun, Nigeria. Total length and body weight of all samples measured and samples were grouped based on length into sizes: juveniles (10-14.9 cm), sub-adults (15.1-19.9 cm), and adults (20.2-26.3 cm). Significant differences (p<0.05) were observed in the meristic characters in all the groups. Dorsal fin ray ranged from 7-9, pelvic fin ray 8-12, caudal fin ray 18-24, pectoral fin ray 7-12, anal ray 12-14 and dorsal spine 0-9 through the wet and dry season for all sizes. Length-Weight relationship for juveniles, sub-adult and adult sizes showed ‘a', ‘b' and ‘r' values for juveniles as -0.82, 2.17 and 0.85,  sub-adult as -0.38, 1.82 and 0.90 and adult as 0.44, 1.03 and 0.78 respectively. Mean condition factor recorded was 1.16±0.15, 1.39±0.13, and 2.17±0.59 for adult, sub-adult and juvenile respectively. Conclusively, B. macrolepidotus in this aquatic ecosystem could be in a good environment and quality as condition factor of all sizes were above 1.