Sesamol, a pure compound of sesame, has been reported to have antitumor effects. In the present study, the apoptotic and steroidogenic effects of sesamol on MA-10 cells, a mouse Leydig tumor cell line, was investigated by morphological observations, cell viability assay, flow cytometry analysis, radioimmunoassay, and immunoblotting assay. We found that the number of rounded-up cells increased as the treatment duration of sesamol increased from 3 to 24 h and that the plasma membrane blebbing phenomenon could be observed after 12 h of treatment. In the cell viability assay, the cell surviving rate significantly decreased as the dosage and duration of sesamol treatment increased (p<0.05). Moreover, cell cycle studies illustrated that the percentages of subG1 phase cells significantly increased after 1 mM sesamol treatments for 12 h, and 0.1 and 1 mM sesamol treatments for 24 h, respectively (p<0.05). Furthermore, 0.1 mM sesamol for 24 h and 1 mM sesamol for 12 and 24 h treatments, respectively, significantly induced the cleavage of caspase-3 (p<0.05). These results confirmed the apoptotic event of sesamol treatment on MA-10 cells. Meanwhile, we also found that sesamol at 1 mM for 24 h and 10 mM for 12 and 24 h significantly increased progesterone production (p<0.05), and 1 mM sesamol for 24 h treatment significantly activated the expression of steroidogenic acute regulatory (StAR) protein (p<0.05). However, the expression of P450scc enzyme remained no different among all treatments (p>0.05). In conclusion, sesamol could concurrently induce apoptosis through the activation of the caspase pathway and steroidogenesis through the induction of StAR protein expression in MA-10 mouse Leydig tumor cells.