Trypsin from the viscera of sierra (Scomberomorus sierra) was purified by affinity chromatography on Sepharose-4B coupled to soybean trypsin inhibitor and characterized with respect to its purity, sensitivity to temperature, pH and inhibition. Trypsin was purified from sierra viscera with 11.9-fold and 29.7% yield. The enzyme had a molecular weight of 25.4kDa estimated by SDS-PAGE and two possible trypsin isoforms were observed in activity gels. Trypsin activity was strongly inhibited by soybean trypsin inhibitor and porcine trypsin inhibitor, showing a partial inhibition by a serine protease inhibitor. The optimal activity of the enzyme was observed at pH9 and 60C with n-α-benzoyl-dl-arginine-p-nitroanilide as a substrate. The enzyme maintained more than 50% of its activity in temperatures up to 50C and within the pH range of 8-10 for a period of up to 2h.