The increasing cost and unpredictable availability of fishmeal and anti-nutritional factors of plant proteins necessitates the search on cheap and abundantly available protein source with capabilities of growth promotion. The feeding trial was conducted to evaluate the effect of hydrothermically processed soybean on growth performance, intestinal enzymatic activity and carcass composition for which three diets were formulated T 1 , T 2 , T 3 containing fish meal, raw soybean, and processed soybean, respectively. Cirrhinus mrigala fingerlings were stocked in glass aquaria (60×30×30cm)/ plastic tubs (50L) for each diet in triplicates. Fingerlings were fed twice daily @ 4% of wet body weight for 90 days. Length-weight measurements were done fortnightly to adjust the feed quantity. Significantly (P<0.05) high growth performance and low FCR were observed in the fingerlings fed with diet containing processed soybean. Crude protein (%), crude fat (%) and gross energy (kJ g -1 ) were found to be significantly (P<0.05) high in the carcass of fish fed with T 3 . Intestinal enzymatic activities were also significantly higher in the group T 3 than to those fed on fish meal and raw soybean. The excretion of ammonia and reactive phosphate was also low with the inclusion of processed soybean, indicating the good quality of water. Therefore, the use of hydrothermically processed soybean in the diets can help in substituting fish meal protein without compromising growth and digestibility parameters and the use of processed soybean in the diets can also eliminate or reduce the pollution problems associated with intensive aquaculture system.