Some of the effects of tumor necrosis factor alpha (TNF-α) are suggested to be mediated by oxidative stress. It has also been reported that dietary supplements of olive oil result in a reduction in LDL, oxidative stress, and blood pressure and these effects are attributed to oleic acid (OA)-a major component of olive oil. The objective of this study was to examine the beneficial effects of OA against TNF-α-induced oxidative stress and cardiomyocytes injury. Isolated cardiomyocytes from adult rat hearts were treated as follows: (A) control; (B) OA (50 μM); (C) TNF-α (10 ng/ml); and (D) TNF-α + OA. After 4 h of the treatment, cells were assessed for oxidative stress, cellular damage, viability, and apoptosis. Cardiomyocytes treated with TNF-α showed a significant increase (P < 0.05) in reactive oxygen species, decrease in the viability of cells, and increase in creatine kinase release. All these TNF-α-induced changes were prevented by OA. TNF-α also caused a significant increase in the expression of apoptotic proteins Bax, Caspase 3 and PARP cleavage, Bnip3, and TGF-β , whereas OA modulated these changes. It is suggested that TNF-α induced oxidative stress mediates cardiomyocyte cell damage which is prevented by OA.