The effect of fermented Tamarindus indica seed nut on the composition, growth, nutrient utilisation and carcass composition of Oreochromis niloticus fingerlings fed graded levels of fermented T. indica seed meal was investigated for 84 days. Fermentation significantly increased the crude protein and lipid content of the seeds by 10.17 and 46.62%, respectively while alkaloid, saponin and phytate content of the seeds were reduced by 59.46, 21.74 and 60.30%, respectively. Five diets were formulated to include 0, 25, 50, 75 and 100% inclusion of fermented T. indica seed meal. The results for growth and feed utilisation revealed that the best experimental diet was the 75% inclusion level, as it gave the best mean weight gain (8.58g), standard length gain (2.54cm), total length gain (3.12cm), specific growth rate (0.85%days), percentage weight gain (1.01) and nitrogen metabolism (194.60) compared with the other diets. Carcass composition showed that all fish fed experimental diet had an increase in carcass crude protein and ranged between 49.99-54.02% compared to the initial of 43.91%. Thus the use of T. indica seed at 75% replacement level of soya beans seed is recommended in the diet of O. niloticus fingerlings.