Adenocalymma alliaceum (A. alliaceum) is well known for its traditional medicinal uses and as a substitute for garlic. The methanol extract from A. alliaceum flowers (AAF) was investigated for its growth inhibitory activity on the estrogen receptor positive MCF-7 and estrogen receptor negative MDA-MB231 breast cancer cells by MTT assay. Treatment of breast cancer cells with different concentrations of AAF resulted in dose dependent growth inhibition with a growth inhibitory concentration (GI50) of 53.1±4.1 lg/mL in MCF-7 and 23.9±3.7 lg/mL in MDA-MB-231 cells. Treatment of breast cancer cells with AAF resulted in time-dependent sequence of events marked by apoptosis, as shown by translocation of phosphatidylserine and activation of caspase-3. Analysis of data suggests that AAF exerts growth inhibition on both breast cancer cells through apoptosis induction, and that it may contain potent anticancer secondary metabolites valuable for application in drug products.