Obesity, a condition characterized by increased fat content and altered secretion of adipokines, is a risk factor for postmenopausal breast cancer. Visfatin has recently been established as a novel adipokine that is highly enriched in visceral fat. Here we report that visfatin regulated proliferation of MCF-7 human breast cancer cells. Exogenous administration of recombinant visfatin increased cell proliferation and DNA synthesis rate in MCF-7 cells. Furthermore, visfatin activated G1-S phase cell cycle progression by upregulation of cyclin D1 and cdk2 expression. Visfatin also increased the expression of matrix metalloproteinases 2, matrix metalloproteinases 9, and vascular endothelial growth factor genes, suggesting that it may function in metastasis and angiogenesis of breast cancer. Taken together, these findings suggest that visfatin plays an important role in breast cancer progression.