Marine yeasts isolated from coastal mangrove ecosystem namely Candida albicans, Kuraishia capsulate and Sacchromyces cerevisae were screened for the cytotoxicity against a non-transformed Vero (African green monkey kidney normal cell line) and two cancer cell lines human breast carcinoma cells (HepG2), human breast carcinoma cells (MCF -7) in different concentrations (1000 to 1.953 µg/ml). Lower doses enhanced the viability of the cultured cells, MTT assay .higher doses decreased viability of the cells by 50% or more. MTT assay was used to measure the cell proliferation and survival. Amongst three yeast strains, Sacchromyces cerevisae showed more than 80% cell viability in Vero cell lines and were studied for further cytotoxicity against HepG2, MCF -7 cell lines respectively.