Oxidative stress plays a major role in the pathophysiology of cardiac disorders, but the experimental data on the protective effects of exogenous antioxidants are controversial. A promising cardioprotective strategy may be through the induction of the endogenous antioxidants and phase II enzymes by chemical inducers. Sulforaphane is an isothiocyanate derived from cruciferous vegetables, and it has gained attention mainly as a potential chemopreventive agent in part through the induction of detoxifying enzymes. Accordingly, this study was undertaken to investigate the time-dependent induction of gene transcription, protein expression, and enzyme activity of antioxidant and phase II enzymes [glutathione reductase, glutathione-S-transferase, glutathione peroxidase, NAD(P)H:quinone oxidoreductase-1, thioredoxin reductase] by sulforaphane in cultured rat neonatal cardiomyocytes. The potential cardioprotective action of sulforaphane was confirmed by the decrease in intracellular reactive oxygen species production, the increase in cell viability, and the decrease in DNA fragmentation after long-term treatment accompanied by the induction of antioxidants and phase II enzymes in cardiomyocytes.