A Gram-staining-positive, heterotrophic, anaerobic, non-spore-forming, non-motile, rod-shaped strain, OAct400T, belonging to the genus Microbacterium was isolated from a sediment collected from a depth of 2093 m in the South China Sea, China. The strain was identified using a polyphasic taxonomic approach. The strain grew well on yeast extract/malt extract agar (ISP 2) and nutrient agar media, and formed no aerial mycelium and no diffusible pigments on any media tested. The strain grew in the presence of 0-8 % (w/v) NaCl (optimum, 2-4 %), at pH 5.0-10.0 (optimum, pH 7.0) and at 4-37 °C (optimum, 28 °C). Strain OAct400T contained ornithine as the diagnostic diamino acid. The whole-cell sugars were dominated by glucose and galactose. The predominant menaquinones were MK-11 (51 %) and MK-10 (24 %). The major phospholipids were phosphatidylglycerol and diphosphatidylglycerol. The major fatty acids were anteiso-C15 : 0 (59.35 %), iso-C16 : 0 (17.89 %) and anteiso-C17 : 0 (16.09 %). DNA-DNA relatedness with Microbacterium amylolyticum DSM 24221T and Microbacterium gubbeenense CIP 107184T, the nearest phylogenetic relatives (97.73 and 97.44 % 16S rRNA gene sequence similarity, respectively) was 31.3 ± 2.1 and 28.7 ± 1.2 %, respectively. On the basis of phenotypic, phylogenetic and genotypic data, a novel species, Microbacterium nanhaiense sp. nov., is proposed. The type strain is OAct400T ( = CGMCC 4.7181T = DSM 26811T = KCTC 29185T).