Snake venoms contain a variety of biologically active proteins, which have therapeutic potential. Montivipera wagneri is an endemic mountain viper species of Turkey. In this study, the cytotoxic activity of M. wagneri crude venom was investigated against A549, HeLa, CaCo-2, U-87MG, PC3 and MCF-7 cancerous cells and non-cancerous cells Vero and HEK293 by MTT assay. The IC50 values of M. wagneri crude venom on cultured cells varied from 1.02 +/- 0.02 to 19.76 +/- 0.42 mu g/ml, with the most potent activities against A549 and CaCo-2 cells. The present work documents the venom of M. wagneri for the first time, showing promising results as a potential source for cytotoxic proteins or peptides.