Sixty days feeding experiment was conducted on grass carp fry fed isocaloric diets with variable protein levels in order to evaluate its growth response. Different diet ingredients were analyzed for % age protein, % age fat, % age ash, % fiber, % age moisture contents and energy. Five isoenergetic (17.91 ± 0.02 Kg MJ-1) and isolipidic (8.56 ± 0.09 g) diets with varying protein levels PL1 (20%), PL2 (25%), PL3 (30%), PL4 (35%) and PL5 (40%) were formulated, analyzed and fed to triplicate groups of fish fry each group comprised of 10 fish (average weight 0.57 ± 0.001g fish-1). Experimental design was a completely randomized design. Highest mean weight gain, average daily growth, final weight gain, specific growth rate but lowest feed conversion ratio were observed (P<0.05) in fish fed diet PL5 (40% protein level diet). Whereas significantly lowest mean weight gain, average daily growth, percent weight gain, specific growth rate but highest feed conversion ratio (P<0.05) were observed for PL1 (20% protein level diet). Average temperature (29.66–30.0 ºC), pH (8.32–8.55), dissolved oxygen (6.31-6.60 mg/L) were within the optimum range throughout the experiment and did not significantly differ among different treatments (P<0.05). Present study revealed that forty percent protein level is best and economical for rearing grass carp fry.