Abstract: Ionizing radiation can induce cell damage by generating reactive oxygen species (ROS). The present study was carried out to investigate the radio-protective effects of a flavonoid compound, morin (2′,3,4′,5,7-pentahydroxyflavone) and the underlying mechanisms. Morin was found to reduce the intracellular ROS generated by γ-irradiation. Moreover, morin protected cellular components against radiation-induced membrane lipid peroxidation and cellular DNA damage, which are the main targets of radiation-induced cell damage. Morin recovered cell viability damaged by radiation via inhibition of apoptosis. Irradiated cells with morin treatment reduced Bax, phospho Bcl-2, active caspase 9 and caspase 3, which were induced by γ-radiation. Irradiated cells with morin recovered the expression of Bcl-2 reduced by γ-radiation. Morin exerted anti-apoptotic effects via inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1)-c-Jun NH2-terminal kinase (JNK)-activator protein 1 (AP-1) cascades induced by γ-radiation. The results suggest that morin protects cells against oxidative stress induced by radiation via reduction of ROS and attenuation of SEK1-JNK-AP-1 pathway.