In this study, we investigated the antioxidant capacity of persimmon wine (PW) and dealcoholized persimmon wine (DPW). Both PW and DPW showed radical scavenging activity in the DPPH (1-diphenyl-2-picrylhydrazyl) assay. We next analyzed the phenolic content and major compounds present in PW using high-performance liquid chromatography (HPLC). Phenolic compounds, including gallic acid, catechin, and epicatechin, were found in PW. Gallic acid was the most abundant phenolic compound (157.5 µg/ml) in PW. In addition, the protective effects of DPW and gallic acid against H₂O₂-induced cell injury in H9c2 cardiomyocytes were investigated. Pretreatment with DPW or gallic acid strongly inhibited H₂O₂-induced cell death in a dose-dependent manner. These results suggested that PW and its major phenolic component, gallic acid, were effective inhibitors of oxidative stress and oxidative stress-induced cardiomyocyte injury.