Abstractβ‐Asarone is the predominant component of the essential oil of rhizomes of Acorus calamus Linn ( Sweet flag). Although rhizome extracts from this plant have long been used for insect pest control, their cytotoxic effects on insect cells are not well understood. In this study, we evaluated the potency of β‐asarone as a natural insecticide by using a Spodoptera frugiperda cell line (Sf9). To assess the cytotoxic effects of β‐asarone on Sf9 cells, we observed morphologic changes in treated cells and performed a cell proliferation assay and a DNA fragmentation assay. After 24 and 48 h of treatment with β‐asarone, the proliferation of the Sf9 cells was inhibited in a dose‐dependent manner, with IC50 values of 0.558 mg/ml at 24 h and 0.253 mg/ml at 48 h. Morphologic changes in β‐asarone‐treated cells were typical of apoptosis and included loss of adhesion, cell shrinkage, and small apoptotic bodies. The DNA laddering present in β‐asarone‐treated SF9 cells and annexin V assay confirmed that this compound can induce apoptosis in insect cells. Together, these findings suggest that apoptosis induction may be one mechanism through which β‐asarone inhibits the proliferation of insect cells and thus exerts insecticidal effects.