Objective: Envenomation by heamotoxic snakes constituted a critical health occurrence in the world. Bleeding is the most sever consequence following snake bite with viperid and crothalid snakes. It is believed that the degradation of vascular membrane caused hemorrhage; in contrast, some suggested that direct cytotoxicity has role in endothelial cell disturbances. This study was carried out to evaluate the direct toxicity effect of V. LEBETINA crude venom on Human Umbilical Vein Endothelial Cells (HUVECs). Methods: The effect of V. LEBETINA snake venom on HUVECs growth inhibition was determined by MTT assay and neutral red uptake assay. The integrity of cell membrane through LDH release was measured with the Cytotoxicity Detection Kit. Morphological changes of endothelial cells were also evaluated using a phase contrast microscope. Result: In MTT assay, crude venom showed a cytotoxic effect on endothelial cells which was confirmed by the effect observed with neutral red assay. Also, crude venom caused changes in the integrity of cell membrane by LDH release. The morphological alterations enhanced in high concentration results in total cells number reduced. Conclusion: V. LEBETINA venom showed potential direct cytotoxic effects on human endothelial cells in a manner of concentration-dependent inhibition.