Resveratrol (RSV), a natural antioxidant that is contained a lot in red wine or the grape skin, has beneficial effects on cardiac and skeletal muscles such as anticancer, antiviral, neuroprotective, anti-aging, and life-extending, and therefore is widely used for the improvement of human health and the prevention of diseases. Aging is a significant risk factor for cardiovascular diseases, and mitochondrial dysfunction plays a critical role in the pathologic mechanisms of cardiac failure or diseases with aging. Therefore, the purpose of this study was to determine whether the resveratrol attenuates aging-induced mitochondrial dysfunction in rat cardiac muscle. Fischer 344 rats were divided into young sedentary (YS; n=10, 4 months) group, young resveratrol (YR; n=10, 4months) group, old sedentary (OS; n=10, 20 months) group, and old resveratrol (OR; n=10, 20 months) group. Rats were treated with RSV (50mg/kg/day) via oral gavage for 3 weeks. Left ventricle was extracted to determine mitochondrial O2 consumption (respiration) with Oroboros O2K Oxygraph and mitochondrial H2O2 emission and Ca2+ retention capacity with Spex Fluormax 4 spectrofluorometer. Resveratrol treatment attenuated age-induced increase in cardiac muscle mass in old groups. Mitochondrial O2 respiratory capacity was decreased by aging and was protected by RSV treatment. Mitochondrial Ca2+ retention capacity was decreased by aging and was protected by RSV treatment in the old groups. RSV treatment attenuated age-induced mitochondrial H2O2 emitting potential in the heart. These data demonstrate that resveratrol protects against aging-induced impairment of mitochondrial function in cardiac muscles. In addition, these data imply that resveratrol may attenuate aging-induced cardiac dysfunction by reducing oxidative stress in aged cardiac muscle.