The objective of this research was to evaluate the effect of adding protected protease to low-amino acids (AA) diets on the growth performance of barrows. Three decreasing levels of AA (protein levels), with or without the addition of protease were fed to 48 hybrid barrows (27.42±3.48 kg initial body weight). The experimental design was a completely randomised with a factorial arrangement of treatments. An analysis of variance was performed with GLM of SAS and the means comparison was performed with Tukey test (P≤0.05). The productive performance was not affected by addition of proteases in the diet at the three stages (P>0.05). Only in growing barrows, the interaction of standard protein diet and protease reduced backfat thickness (P≤0.05). Protein level in finishing I barrows did not affect (P>0.05) growth performance variables. Low-protein diets increased (P≤0.05) average daily gain, final body weight and fat-free lean gain in growing and finishing II barrows. Concentration of urea in plasma decreased with the reduction of CP and increased with the addition of protease (P≤0.05) at the three stages. In conclusion, low protein diets improved or maintained growth performance variables and reduced the plasma urea nitrogen, whereas supplementation with protease did not show any effect on productive performance.The objective of this research was to evaluate the effect of adding protected protease to low-amino acids (AA) diets on the growth performance of barrows. Three decreasing levels of AA (protein levels), with or without the addition of protease were fed to 48 hybrid barrows (27.42±3.48 kg initial body weight). The experimental design was a completely randomised with a factorial arrangement of treatments. An analysis of variance was performed with GLM of SAS and the means comparison was performed with Tukey test (P≤0.05). The productive performance was not affected by addition of proteases in the diet at the three stages (P>0.05). Only in growing barrows, the interaction of standard protein diet and protease reduced backfat thickness (P≤0.05). Protein level in finishing I barrows did not affect (P>0.05) growth performance variables. Low-protein diets increased (P≤0.05) average daily gain, final body weight and fat-free lean gain in growing and finishing II barrows. Concentration of urea in plasma decreased with the reduction of CP and increased with the addition of protease (P≤0.05) at the three stages. In conclusion, low protein diets improved or maintained growth performance variables and reduced the plasma urea nitrogen, whereas supplementation with protease did not show any effect on productive performance.