The present research work was conducted to evaluate the effect of phytase supplementation on growth and nutrient digestibility of the Catla catla fingerlings fed Moringa oleifera leaf meal (MOLM) based diet. The phytic acid’s presence in plant by-products decreases the bioavailability of nutrients to fish, resulting in poor fish growth and low nutrient digestibility in the body. Experimental diet was divided into six groups and were supplemented with graded levels (0, 300, 600, 900, 1200 and 1500 FTU kg-1) of phytase. Cr2O3 was incorporated in all diets at the rate of 1% as a non-digestible marker. The fingerlings were fed at the rate of 4% of live wet weight twice a day and faeces were collected from each tank. On the basis of results it was noted that phytase supplementation showed significant (p<0.05) improvement in growth indices (WG%, FCR, SGR) and digestibility of nutrients (i.e. CP, EE and GE) when C. catla fingerlings were fed at 900 FTU kg-1 level in MOLM based diet. It was further noted that phytase supplementation decreased the discharge of nutrients through faeces resulting in reduced eco-pollution. On the basis of results it was concluded that phytase supplementation at 900 FTU kg-1 level was helpful to develop a cost-effective as well as eco-friendly fish feed by using MOLM based diet.