Abstract: Oreochromis andersonii were maintained on three formulated diets based on protein levels (20, 30 and 40%) with soya bean as the source. The effect of dietary protein on growth and feed utilization were investigated. The cost effectiveness of the diets was also evaluated. Both the Body Weight Gain (BWG) and final mean weight of fish maintained on 30% protein were not significantly different (p>0.05) from the fish fed with 40% protein diet. The Protein Efficiency Ratio (PER) declined with protein increase (r = -0.282, n = 268, p<0.05). There was a linear relationship (Y = 0.318x + 12.79, r2 = 0.97) between protein level and BWG. Gross margin for fish reared on 30% and 40% crude were insignificant (p>0.05) though significantly higher than the 20% crude protein fed fish and the control. The carcass protein composition was not affected (p>0.05) by the protein level. The 30% soyabean based crude protein is recommended for O. andersonii.