α-Asarone is the main component of Acorus gramineus, which is a widely used oriental traditional medicine. A. gramineus is known to have a variety of medicinal effects, such as anti-gastric ulcer, antiallergy and antioxidant activity. It is also known to inhibit the release of histamine. However, the mechanism of its action remains unclear in humans. In this study, the effects of α-asarone on matrix metalloproteinase (MMP) and its antioxidant effect in a cell-free system were examined in HT1080 cells. In an MTT assay, the effect of α-asarone on cell viability showed no cytotoxicity below 16 μM. In an antioxidant assay, α-asarone increased reducing power in a dose-dependent manner but not the scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. In addition, α-asarone exhibited the protective effect against DNA oxidation induced by hydroxyl radicals produced by the Fenton reaction. Furthermore, in a gelatin disk assay, α-asarone enhanced collagenase activity. It also increased the activities of MMP-2 and MMP-9 stimulated by phorbol 12-myristate 13-acetate (PMA) in a gelatin zymography. On the other hand, the activity of MMP-9 stimulated by phenazine methosulfate (PMS) but not that of MMP-2 was increased in the presence of α-asarone. These findings suggest that α-asarone could be a candidate for the prevention and treatment of pathological diseases related to oxidative stress and MMPs.