An actinomycete strain 232617(T) was isolated from a composite mangrove sediment sample collected in Haikou, China. Phylogenetic analysis of the 16S rRNA gene sequence of strain 232617(T) indicated the highest similarity with Micromonospora siamensis TT2-4(T) (99.05%), Micromonospora krabiensis A-2(T) (98.99%) and Micromonospora carbonacea DSM 43815(T) (98.91%). The gyrB gene sequence analysis also indicated that 232617(T) should be assigned to the genus Micromonospora. The cell wall contains meso-DAP and glycine. The major menaquinones were MK-10(H(4)) and MK-10(H(6)), with MK-9(H(4)) as minor components. The characteristic whole-cell sugars are xylose, arabinose and glucose. The phospholipid profile comprises phosphatidylethanolamine, diphosphatidlglycerol and phosphatidylinositol mannoside. The DNA G+C content is 71.5 mol%. Furthermore, a combination of DNA-DNA relatedness and some physiological and biochemical properties indicated that the novel strain could be readily distinguished from the closest related species. On the basis of these phenotypic and genotypic data, strain 232617(T) represents a novel species of the genus Micromonospora, for which the name Micromonospora haikouensis sp. nov. is proposed. The type strain is 232617(T) (= CCTCC AA 201112 (T) = DSM 45626 (T)).