Two experiments were carried out to evaluate the effect of using soy protein concentrate (SPC) in pre-starter and starter diets for broilers. In the first experiment, 600 male Cobb broilers, between one and 40 days of age, were distributed in a completely randomized design, with four treatments and six replications of 25 birds each. Treatments were ofered to broilers in the pre-starter and starter diets and consisted of inclusion of soy protein concentrate (0,3,6 and 9%) in diets. The parameters evaluated were: body weight gain, feed conversion ratio, consumption of ration, enzyme production in the pancreas, villus: crypt ratio, leukocyte count and immunoglobulin A (IgA) dosage. Aimed to determine the coefficient of nutrient metabolization of feeds, 144 male Cobb chicks were distributed, between 14 and 21 days of age, with four treatments and six replications of six birds per experimental unit. Treatments were the same as in the first experiment. The use of 3 and 9% of SPC did not affect weight gain, feed intake, feed conversion or viability of the poultry. The use of 6% of SPC provided an increase in trypsin activity, villi length and crypt depth; the coefficient of dry matter metabolization increased linearly; but no differences were observed in performance or immunological parameters.