A 90 days growth trial was conducted to evaluate optimum protein requirement for Indian spiny loach (Lepidocephalus thermalis). Five different protein feeds viz., 20%, 25%, 30%, 35%, and 40% were prepared as experimental diets. This feeding trial was conducted in 40 L plastic troughs in triplicates using loaches with an average weight of 1.28 g - 1.55 g. During the experimental period, water quality parameters were measured and recorded daily. The mean value of water temperature, pH, dissolved oxygen, ammoniaN, nitrite-N, nitrate-N, hardness, alkalinity in the experimental system were 23.5-26.3°C, 8.5-8.7, 5-6 ppm, 0.01 ppm, 0.05 ppm, 10 ppm, 650 ppm, 165 ppm respectively. Among the experimental diets 35% protein diet yielded the best result in terms of average body weight gain, PER, SGR and ADG. The mean body weight gain recorded in the 35% protein diet was 0.67 ± 0.008 g. In this study, 35% protein feed performed well in terms of growth rate and PER hence it is recommended that the optimum protein requirement for the better growth o