Momordica charantia has been used traditionally for the treatment of several ailments. Some natural plant products are known to exhibit cytotoxic or anti-proliferative effects on cancer cell lines, such plants offer a promising therapeutic approach as an anti-tumor agent. In this study, the anti-proliferative effects of graded concentrations of methanol leaf extract of M. charantia (MEMC) at different point time was examined on vascular smooth muscle cells (VSMC), and human colorectal adenocarcinoma cell lines (HT-29) were investigated using the MTT proliferation assay. The result showed that after 24 and 48 h, the effect of MEMC on the VSMC alone and in the presence of the mitogens was more of proliferation. In the case of HT 29 cytotoxic study, the extract at all doses used caused a cytotoxic effect. The effect of the extract of M. charantia was more pronounced and consistent at 72 h time point exhibiting cytotoxic actions against cancer cell lines, the extract showed no toxic action to normal cells. This suggests a possible use of the plant M. charantia to identify compounds of possible interest in the treatment of cancer. While the extract possesses proliferative effects on the VSMCs, the reverse is the case, where it exhibited cell inhibitory effects on HT 29 cell lines indicating that the plant exhibit cytotoxic effects and could then serve as lead agents in the search for anticancer drugs from natural products.