Abstract: Leaves of Cayratia carnosa have been ethnomedically claimed to possess a wide array of biological activities including anticancer activity. To verify the folklore claim, this study was performed in a Human breast carcinoma cell lines, MCF-7 and MDA-MB-231. Methanol and aqueous extracts of the leaves of C. carnosa showed cytotoxic effect on MCF-7 and MDA-MB-231 cell line, as determined with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) microculture tetrazolium viability assay. Subcellular alterations were evaluated by using normal inverted microscope. Cells treated with methanol extract showed degeneration of cytoplasmic organelles, profound shrinkage of cells and apoptotic characteristics. The results showed that the methanol extract possesses cytotoxic effect which was greater than aqueous extract when compared to that of the control.