Age-related alterations in the renin-angiotensin-aldosterone system (RAAS) have been reported in the cardiovascular system; however, the detailed mechanism of the RAAS component mineralocorticoid receptors (MR) has not been elucidated. The present study aimed to investigate the associations between MR and cardiac aging in rats, as well as the regulatory effects of oxidative stress and mitochondrial abnormalities in the aging process. MR expression in the hearts of male Sprague-Dawley rats aged 3 months (young rats) and 24 months (old rats) was evaluatedin vivo. In addition,in vitro, H9C2 cells were treated with a specific MR antagonist, eplerenone, in order to investigate the molecular mechanism underlying the inhibition of myocyte aging process. The results demonstrated that MR expression was significantly higher in 24-month-old rat hearts compared with in 3-month-old rat hearts. These changes were accompanied by increased p53 expression, decreased peroxisome proliferator-activated receptor gamma coactivator-1 alpha expression, decreased mitochondrial renewal as assessed by electron microscopy, increased oxidative stress and decreased superoxide dismutase.In vitro, selective antagonism of MR partially blocked H2O2-induced myocardial aging as assessed by p16, p21 and p53 expression levels and excessive reactive oxygen species (ROS) accumulation. These results indicated that increased MR expression may drive age-related cardiac dysfunction via mitochondrial damage, increased ROS accumulation and an imbalanced redox state.