A 60-day feeding experiment was conducted in the laboratory to evaluate the interactive effects of dietary protein and carbohydrate levels on growth, feed utilization efficiency, and nitrogen metabolism in rohu, Labeo rohita fingerlings (mean weight 4.06 ±0.08 g). Nine purified diets prepared with 25, 35, and 40 % protein level each having 15, 25, and 35 % carbohydrate were fed to nine different feeding groups at the rate of 3% of body weight in triplicate treatments. Better performance of fish in terms of percent weight gain, SGR, FCR, and PER was observed with increasing percentage of carbohydrate at a given protein level. Protease and α-amylase activities increased with increase in dietary protein and carbohydrate levels, respectively. Glutamate oxaloacetate transaminase (GOT) activities varied significantly in some groups. No significant difference among different groups regarding glutamate pyruvate transaminase (GPT) activity was observed. Ammonia excretion was found to increase with increased consumption of dietary protein and carbohydrate and was highest in the groups of fish fed 40% protein diet suggesting active nitrogen metabolism in these.