Dietary prevention has been known to reduce breast cancer risk. Sesamin is one of the major components insesame seeds and has been widely studied and proven to have anti-proliferation and anti-angiogenic effects oncancer cells. In this study, the influence of sesamin was tested in the human breast cancer MCF-7 cell line forcell viability (MTT assay) and cell cycling (flow cytometry). Results showed that sesamin dose-dependently (1,10 and 50 μM) reduced the cell viability and increased LDH release and apoptosis (TUNEL assay). In addition,there was a significant increase of sub-G1 phase arrest in the cell cycle after sesamin treatment. Furthermore,sesamin increased the expression of apoptotic markers of Bax, caspase-3, and cell cycle control proteins, p53 andcheckpoint kinase 2. Taken together, these results suggested that sesamin might be used as a dietary supplementf or prevention of breast cancer by modulating apoptotic signal pathways and inhibiting tumor cell growth.