Traditional treatments of cancer include surgery, chemotherapy, radiotherapy, hormone therapy, and combination therapy which affect both cancer and normal cells. The present study investigated anticancer venom potentials of Montivipera xanthina and Leiurus quinquestriatus compared to the synthetic anti-estrogen drug (Tamoxifen®) on MCF-7 breast cancer cell line. Cytotoxicity of venoms was evaluated using MTT assay. Cell cycle arrest was done using propidium iodide DNA stained by Flow Cytometry. Apoptosis was determined using annexin V-FITC by Flow Cytometry. Gene expression analysis was done for Caspase3, HER2, ER, and Survivin using qRT-PCR 24hrs post treatment and histological examination. L. quinquestriatus & M. xanthina venoms and tamoxifen had IC50 at 2.5, 34.4 & 27.8μg/mL with MCF-7 cell line respectively. Cell cycle was ceased at G1/S phase of L. quinquestriatus and M. xanthina compared to tamoxifen. In gene expression analysis, venoms and tamoxifen exhibited apoptotic effect against MCF-7 cell lines by elevated expression of Caspase3 & depletion of HER2, ER, and Survivin. Histological examination showed apoptotic and slightly necrotic features in both venoms. Tamoxifen induced a number of apoptotic bodies and colonies of necrotic cells