<jats:title>Abstract</jats:title><jats:p>Actinobacteria from the unique intertidal ecosystem of the mangroves are known to produce novel, bioactive secondary metabolites. A novel strain known as MUSC 136<jats:sup>T</jats:sup> (=DSM 100712<jats:sup>T</jats:sup> = MCCC 1K01246<jats:sup>T</jats:sup>) which was isolated from Malaysian mangrove forest soil has proven to be no exception. Assessed by a polyphasic approach, its taxonomy showed a range of phylogenetic and chemotaxonomic properties consistent with the genus of <jats:italic>Streptomyces</jats:italic>. Phylogenetically, highest similarity was to <jats:italic>Streptomyces misionensis</jats:italic> NBRC 13063<jats:sup>T</jats:sup> (99.6%) along with two other strains (>98.9% sequence similarities). The DNA–DNA relatedness between MUSC 136<jats:sup>T</jats:sup> 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 <jats:italic>Streptomyces malaysiense</jats:italic> sp. nov. is proposed. The potential bioactivities of this strain were explored by means of antioxidant and cytotoxic assays. Intriguingly, MUSC 136<jats:sup>T</jats:sup> exhibited strong antioxidative activities as evaluated by a panel of antioxidant assays. It was also found to possess high cytotoxic effect against HCT-116 cells, which probably mediated through altering p53 protein and intracellular glutathione levels. Chemical analysis of the extract using GC-MS further affirms that the strain produces chemopreventive related metabolites.