The development of diabetic cardiomyopathy is attributed to diabetic oxidative stress, which may be related to the mitogen activated protein kinase (MAPK) c-Jun N-terminal kinase (JNK) activation. The present study tested a hypothesis whether curcumin analog, C66 [(2E,6E)-2,6-bis(2-(trifluoromethyl)benzylidene) cyclohexanone] as a potent antioxidant can protect diabetes-induced cardiac functional and pathogenic changes via inhibition of JNK function. Diabetes was induced with a single intraperitoneal injection of streptozotocin in male C57BL/6 mice. Diabetic and age-matched control mice were randomly divided into three groups, each group treated with C66, JNK inhibitor (JNKi, sp600125) or vehicle (1% CMC-Na solution) by gavage at 5mg/kg every other day for three months. Neither C66 nor JNKi impacted diabetic hyperglycemia and inhibition of body-weight gain, but both significantly prevented diabetes-induced JNK phosphorylation in the heart. Compared with basal line, cardiac function was significantly decreased in diabetic mice at 3 months of diabetes, but not in C66- or JNKi-treated diabetic mice. Cardiac fibrosis, oxidative damage, endoplasmic reticulum stress, and cell apoptosis, examined by Sirius-red staining, western blot, and thiobarbituric acid assay, were also significantly increased in diabetic mice, all which were prevented by C66 or JNKi treatment under diabetic conditions. Cardiac metallothionein expression was significantly decreased in diabetic mice, but almost normal in C66 or JNKi treated diabetic mice. These results suggest that like JNKi, C66, is able to prevent diabetic up-regulation of JNK function, resulting in a prevention of diabetes-induced cardiac fibrosis, oxidative stress, endoplasmic reticulum stress, and cell death, along with a preservation of cardiac metallothionein expression.