Some aspect of the biology of Tilapia mariae from lower River Ogun, Akomoje water reservoir with emphasis on its food habits were studied between the months of February and June. A total number of 100 fish specimens were collected on monthly basis from the landings of artisanal fishermen around the water body. The length and weight relationships and the well being of the species were investigated. The contents of their stomach were examined.  Mean standard lengths of fish sample were ranged from 15.12±0.81cm in male while female ranged from 17.83±0.76. The species from this water body revealed negative allometry growth pattern. There was variation in condition factor (k) for both sexes. The well being of the females revealed better condition than the males in all months of study. The results of monthly variation in food items showed that Bacillariophyta, Chlorophyta, Cyanophyceae, Crustacean, Detritus, plant tissues, and unidentified food all occurred in varying quantities from February to June. Bacillariophyta (diatoms) appeared as the dominant food of Tilapia mariae accounting for 14.72% and 78.10% by number and occurrence. Cyanophyceae constituted 11.43% and 59.63% by number and occurrence and was second most important food item. Crustaceans occurred least in order of importance (2.34% in numbers and 27.12% in frequency of occurrence. The sex ratios of Tilapia mariae in the Reservoir was 1:3.12 (M:F), with highest abundance of females in March (1:3.17) and April showing the least 1:2.05 (M:F). The study concludes that there is large population of algae in the water body. It also confirms the herbivorous feeding habit of the species.