Sesamin, an active ingredient of Asiasarum heterotropoides, is known to exhibit many bioactive functions, but the effect thereof on vascular smooth muscle cells (VSMCs) proliferation remains poorly understood. Hence, we explored the anti-proliferative action of sesamin on VSMCs and the underlying mechanism thereof, focusing on possible effects of sesamin on cell cycle progression. Sesamin significantly inhibited platelet-derived growth factor (PDGF)-induced VSMCs proliferation (inhibition percentage at 1, 5, and 10 μM sesamin were 49.8 ± 22.0%, 74.6 ± 19.9%, and 87.8 ± 13.0%, respectively) in the absence of cytotoxicity and apoptosis, and PDGF-induced DNA synthesis; and arrested cell cycle progression in the G0/G1-to-S phase. Sesamin potently inhibited cyclin D1 and CDK4 expression, pRb phosphorylation, and expression of the proliferating cell nuclear antigen (PCNA); and up-regulated p27KIP1, p21CIP1, and p53. The results thus indicate that the anti-proliferative effect of sesamin on PDGF-stimulated VSMCs is attributable to arrest of the cell cycle in G0/G1 caused, in turn, by up-regulation of p27KIP1, p21CIP1, and p53, and inhibition of cyclin E-CDK2 and cyclin D1-CDK4 expression.