The mangrove forest hosts rich assemblages of microorganisms which is exposed to harsh environment settings such as high temperature, high salinity, strong winds and constant tidal gradient fluctuations. These factors are believed to be the driving force that promotes emergence of novel species by encouraging metabolic pathway adaptations and production of valuable metabolites. A novel strain known as MUSC 136T (=DSM 100712T = MCCC 1K01246T) which was isolated from Malaysian mangrove forest soil has proven to be no exception. Assessed by a polyphasic approach, strain MUSC 136T showed a range of phylogenetic and chemotaxonomic properties consistent with the genus of Streptomyces. Phylogenetically, highest similarity was to Streptomyces misionensis NBRC 13063T (99.6%), followed by S. phaeoluteichromatogenes NRRL 5799T (99.6 %) and S. rutgersensis NBRC 12819T (98.9 %); sequences similarities of less than 98.9 % were obtained with the type strains of other species of the genus Streptomyces. The DNA–DNA relatedness between MUSC 136T and these type strains ranged from 22.7 ± 0.5% to 46.5 ± 0.2%. Overall, polyphasic approach studies indicated this strain represents a novel species, for which the name Streptomyces malaysiense sp. nov. is proposed. The potential bioactivities of this strain were explored by means of antioxidant and cytotoxic assays. Intriguingly, MUSC 136T exhibited strong antioxidative activities as evaluated by a panel of antioxidant assays. It was also found to possess high cytotoxic effect against HCT-116 human colon cancer cells, which probably mediated through altering p53 protein and intracellular glutathione levels. Chemical analysis of the extract using gas chromatography-mass spectrometry (GC-MS) further affirms that the strain produces chemopreventive related metabolites.