Oxidative stress has been implicated in the pathogenesis of various cardiovascular diseases, including ischemic heart disease and heart failure. The peroxisome proliferator-activated receptor gamma (PPARγ) agonist improves insulin sensitivity and limits tissue inflammation and cellular apoptosis, but there are few data on the relationship between the PPARγ agonist, rosiglitazone (RSG), and the thioredoxin (TRx) system in oxidatively stressed cardiomyocytes (CMCs). Here we provide evidence that the PPARγ agonist RSG protects rat CMCs from hydrogen peroxide (H2O2)-induced apoptosis by TRx overexpression. The expression levels of pAkt/Akt, pErk/Erk, survivin, Bcl-2/Bax-α, and manganese-superoxide dismutase were increased by RSG pretreatment in H2O2-injured rat CMCs. On the contrary, the expression levels of caspase-3 and p53 were decreased by RSG pretreatment. These effects of RSG were reversed by chemical inhibitors of TRx and the PPARγ antagonist. This suggests that RSG protects rCMCs from H2O2-induced oxidative stress through TRx overexpression and a PPARγ-dependent mechanism.