<p>Background: Malignant melanoma is a highly aggressive malignant melanocytic neoplasm which resists against the most conventional therapies. Sea cucumber as one of marine organisms contains bioactive compounds such as polysaccharide, terpenoid and other metabolites which have anti-cancer, anti-tumor, anti-inflammatory and antioxidant properties. The present study was designed to investigate the anticancer potential of saponin extracted from sea cucumber <em>Holothuria leucospilata</em> alone and in combination with dacarbazine on B16F10 melanoma cell line.<br /> Methods: The B16F10 cell line was treated with different concentrations of saponin (0, 4, 8, 12, 16, 20 <em>&micro;g/ml</em>), dacarbazine (0, 1200, 1400, 1600, 1800, 2000<em> &micro;g/ml</em>) and co-administration of saponin-dacarbazine (1200 da+8 sp, 1200 da+4 sp) for 24 and 48 <em>hr</em> and the cytotoxic effect was examined by MTT, DAPI, acridine orange/propodium iodide, flow cytometry and caspase colorimetric assay.<br /> Results: The results exhibited that sea cucumber saponin, dacarbazine, and co-administration of saponin-dacarbazine inhibited the proliferation of melanoma cells in a dose and time dependent manner with IC₅₀ values of 10, 1400 and 4+1200 <em>&micro;g/ml</em>, respectively. Morphological observation of DAPI and acridine orange/propodium iodide staining documented typical characteristics of apoptotic cell death. Flow cytometry assay indicated accumulation of IC₅₀ treated cells in sub-G1 peak. Additionally, saponin extracted induced intrinsic apoptosis <em>via</em> up-regulation of caspase-3 and caspase-9.<br /> Conclusion: These results revealed that the saponin extracted from sea cucumber as a natural anti-cancer compound may be a new treatment modality for metastatic melanoma and the application of sea cucumber saponin in combination with dacarbazine demonstrated the strongest anti-cancer activity as compared with the drug alone.</p>