The protective effects of methionine against hyperthermia-induced damage in bovine mammary epithelial cells (BMEC) were studied. We have investigated the effects of methionine on proliferation, antioxidant activity, and apoptosis of the mammary epithelial cells of dairy cow after heat treatment. The structure of BMEC membrane was damaged by hyperthermia. Methionine (30 and 60 mg/L) efficiently increased cell viability and attenuated morphological damages in hyperthermia-treated BMEC. It significantly reduced lactate dehydrogenase leakage and malondialdehyde formation, whereas superoxide dismutase activity increased significantly. It also increased cell survival and decreased early apoptosis. Methionine therefore is cytoprotective on hyperthermia-induced damage in BMEC by increasing intracellular antioxidant levels and decreasing lipid peroxidation.