Background: Mimosa pudica belonging to the family Fabaceae , is a small sized shrub, used traditionally for its anti-spasmodic, analgesic, anti-spasmodic, antibacterial, and antitumor activities. Objectives: The present study was conducted to assess the anticancer activity of methanol extract of whole plant of M. pudica (MMP) in MCF-7 and MDA-MB-231 breast cancer cell lines. Materials and Methods: The antitumor activity of MMP was analyzed using 3-(4,5-dimethyl thazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay in MCF-7 and MDA-MB-231 cell lines. The cytological and metabolic alterations due to MMP were evaluated using acridine orange/ethidium bromide dual staining, hoechst 33258 and fluoroprobe, benzimidazol-carbocyanine iodide 5, 5', 6, 6'-tetrachloro-1, 1', 3,3'-tetra ethyl (JC-1) staining. Real-time polymerase chain reaction and Western blotting were carried out to assess Bcl-2, the antiapoptotic gene, and protein expression, respectively. Qualitative analysis and gas chromatography high-resolution mass spectrometry were performed for the presence of various phytochemicals. Results: The methanol extract exhibited a potent antitumor activity in both the cell lines in vitro . Conclusion: The plant extract was showing the mode of action through intrinsic pathway of apoptotic cell death and may be studied further to develop a potent drug against breast cancer.