A Streptomyces strain, MUM256 was isolated from mangrove soil in Malaysia. Streptomyces sp. MUM256 has been identified using phylogenetic analysis based on 16S rRNA sequences. Morphological and biochemical characterization of the strain showed that it has properties consistent with those of the members of the genus Streptomyces. The extract of the fermented culture of MUM256 was prepared with organic solvent extraction method. DPPH, ABTS, ferrous metal chelating, and SOD assays showed MUM256 extract exhibits antioxidant activities. The cytotoxicity of MUM256 extract was determined using cell viability assay against 8 different panels of human cancer cell lines. MUM256 extract showed 2.3-, 2.0-, and 1.8-folds higher inhibitory effect against HCT116, HT29, and Caco-2 respectively when compared to normal cell line at 400μg/mL. The result showed that MUM256 extract was selectively cytotoxic toward colon cancer cell lines. Furthermore, the condensation of chromatin and activation of caspases 3/7 activity are the hallmarks of apoptosis detected using fluorescent microscopy and flow cytometry when HCT116 treated with MUM256 extract. GC-MS analysis resulted in the identification of chemical constituents present in MUM256 extract including phenolic and pyrrolopyrazine compounds which may responsible for antioxidant and anticancer activities observed. This study indicates MUM256 could be a potential source for the development of antioxidative and chemopreventive agents against colon cancer.