Purpose: The present studies were conducted to evaluate the optimum inclusion levels of probiotic Bacillus coagulans, isolated from the intestine of Catla catla for improved growth performance and nutrient retention. Methods: Catla fingerlings (avg. wt. 0.2__ampersandsignplusmn;0.02 g) were fed on isocaloric and isonitrogenous diets supplemented with 2__ampersandsigntimes;104 (D1), 2__ampersandsigntimes;105(D2) and 2__ampersandsigntimes;106(D3) Bacillus coagulans cells 100g-1 of feed for 90 days @ 4 % body weight per day in two equal installments in three replicates. The control treatment (DC) was not supplemented with Bacillus coagulans. Growth and digestibility parameters and intestinal enzyme activities were monitored. Results: The growth of fish in terms of live weight gain (g), growth per day in percentage body weight and specific growth rate were significantly (P__ampersandsignlt;0.05) high in feed D2 in comparison to other dietary treatments. Also, significantly (P__ampersandsignlt;0.05) high values of Apparent protein digestibility (APD), Gross conversion efficiency (GCE) and Protein efficiency ratio (PER) lower FCR (1.64__ampersandsignplusmn;0.02) was observed in the dietary treatment D2. Significantly (P?0.05) high values of digestive enzyme activities (protease, amylase and cellulose), carcass protein, and low excretion of metabolites (ammonia and phosphates) were also observed in feed D2. Conclusion: Results indicated that that supplementation of 2__ampersandsigntimes;105 cells 100g-1of probiotics, B. coagulans could be used to enhance growth performance and nutrient retention of C. catla.