Abstract: A covalent bienzyme superoxide dismutase-chondroitin sulfate-catalase conjugate (SOD-CHS-CAT) demonstrated the dose-dependent inhibitory action on induced aggregation of platelets in the presence of hydrogen peroxide. Antioxidant activity of SOD-CHS-CAT appeared at much lower doses than for other CAT derivatives. We detected the antiaggregation effect of SOD-CHS-CAT for platelet aggregation induced by ADP, serotonin, TRAP (with their different mechanism of action). Novel properties of SOD-CHS-CAT confirmed with its action agains spread-eagle platelets on glass surface. The new characteristics of SOD-CHS-CAT conjugate underline the prospects of its biopharmaceutical development for antioxidant therapy.