A study was conducted to evaluate the effects of supplementation of low protein diets with synthetic methionine and lysine on performance and N economy of broilers. Chicks were allotted to corn-soy diets in a completely randomized design for forty-two days. The diets were 22 and 20% of crude protein (CP) with methionine + lysine content balance and, 22 and 20% CP diets with 110% NRC recommendation of methionine and lysine. Feed intake, daily weight gain, feed conversion ratio (FCR) and mortality showed no significant (P>0.05) treatment effect. However, there was significant improvement (P<0.05) in the performance of birds fed lower (20%) CP diets with synthetic amino acid supplementation, which made it to be at par with those on higher dietary protein (22% CP) level. Similarly, dressing percentage and faecal N were significantly improved (P<0.05) with methionine and lysine supplementation. Serum protein and urea reduced slightly but significantly (P<0.05) with decreasing dietary CP and with methionine and lysine supplementation of the diets. Consequently, the observed trend in serum protein and urea in the present study suggests improved in biological value of the 22% and 20% CP diets with methionine and lysine supplementation. It was, therefore, concluded that to achieve significant improvement in the performance while maintaining considerable reduction in faecal nitrogen of broilers fed CP diets as low as 20%, the diet should be supplemented with methionine and lysine above the levels recommended.