The present study was carried out to investigate the effect of using graded levels of Bio-Nutra 200 and Natuzyme with plant protein diets on the performance of broiler chicks. three dietary levels (0.25, 0.50 and 0.75g/kg) of either Bio-Nutra 200 (probiotic) or Natuzyme (enzyme preparation)  in addition to the control without supplementation were used. Therefore, seven experimental diets were formulated to have similar crude protein and metabolizable energy contents during both starter and grower periods. Three hundred thirty six one-day-old unsexed Hubbard broilers were randomly distributed to seven equal experimental groups. The chicks were fed the experimental starter diets from one day to 21 days of age and switched to feeding the experimental grower diets from 22 to 42 days of age. All chicks were managed similarly and had free access to feed and water during both the starter and grower periods. The criteria of response were live body weight, weight gain, feed intake, feed conversion, economical efficiency of growth, carcass traits, nutrient digestibility [dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), crude fiber (CF) and nitrogen-free extract (NFE), and ash retention], some blood plasma parameters [total protein, albumin and cholesterol , and activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in blood plasma]. The obtained results for the whole experimental period could be summarized as follows: Birds fed either the probiotics- or enzymes-supplemented diets had significantly higher means of final live body weight, weight gain, feed conversion, economic efficiency of growth, nutrient digestibility (i.e. DM, OM and CF), with insignificant differences among them, compared with their control counterparts. In general, birds fed either probiotics- or enzymes supplemented diets achieved significantly higher means of most carcass traits and some blood parameters compared with birds fed control diets; however, AST and ALT were negatively affected. The other criteria were not affected by level of both feed additives. In conclusion, the current study may indicate beneficial effects of adding probiotics and exogenous enzymes (particularly with the level of 0.075 g/ kg) to broiler diets.