This experiment was conducted to evaluate the effect of the addition of a multi enzyme (Natuzyme-P) to corn-soybean based diets and to determine the enzyme's nutrient equivalency on broiler chicks’ performance. Ninety six day-old male broiler chicks were randomly assigned to a number of 24 battery cages in a completely randomized design. The chicks were grown up to 6 wk of age. Six diets (control, negative control, positive control along with three other diets made on the basis of 50, 100 and 120% nutrient equivalency of the enzyme) were formulated and fed to four pens, each pen housing 4 chicks up to 42 days of age. The control diet was formulated with no enzyme supplementation, the positive control diet contained sufficient nutrients for normal broiler growth along with the addition of enzyme as feed additive with an exclusion of the nutrient equivalency of the enzyme and while the negative control diet formulated with no enzyme supplement, but corrected to a nutrient equivalency level for the enzyme. Diets 50, 100 and 120% were prepared together with enzyme supplement and a correction of the diets to 50, 100 and 120% of nutrient equivalency of the enzyme. Body weight gain, feed intake and feed conversion ratio were assessed at 21, 35 and 42 d of age. Results indicated significant differences among the treatments in body weight gain (P<0.01) and feed conversion ratio at 21, 35 and 42 d of age (P<0.05). Carcass, breast, thigh, and abdominal fat relative weights were not affected by the treatments, but gizzard relative weight was. Immune response to PHA-P was significantly affected by treatments (P<¬0.01). In summary, addition of Natuzyme, in comparison with the negative control diet, improved broiler chicks performance, and the treatment with enzyme supplement, accompanied by correction up to 50% of nutrient equivalency of the enzyme resulted in the best response. Correcting up to 50% of nutrient equivalency of the enzyme reduced the feed cost per kg of body weight gain for 4.4 and 5% as compared with the control and positive control diets.