A filamentous actinomycete, designated strain 1SS5-02T, was isolated from mangrove sediment collected from Ranong province, Thailand. The strain formed aerial and substrate mycelia composed of long, branched hyphae. Aerial mycelia differentiated into non-motile, rod-shaped spores. The organism contained meso-diaminopimelic acid and no diagnostic sugars in whole-cell hydrolysates. The predominant menaquinones were MK-11(H4), MK-11(H6) and MK-11(H8). Polar lipids comprised phosphatidylcholine, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, two unidentified phospholipids and four unidentified lipids. The major fatty acids were iso-C16 : 0, C18 : 1ω9c, 10-methyl C18 : 0 and anteiso-C17 : 0. The G+C content of the genomic DNA was 73.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 1SS5-02T belonged to the genus Nocardiopsis. The strain showed the highest degree of 16S rRNA gene sequence similarity with 'Nocardiopsis mangrovei' HA11166 (97.9 %) and Nocardiopsis trehalosi VKM Ac-942T (97.8 %). However, strain 1SS5-02T could be distinguished from its nearest phylogenetic relatives in the genus Nocardiopsis on the basis of DNA-DNA relatedness values and the combination of phenotypic properties. On the basis of polyphasic taxonomy, strain 1SS5-02T is considered to represent a novel species of the genus Nocardiopsis, for which the name Nocardiopsis sediminis sp. nov. is proposed. The type strain is 1SS5-02T (=BCC 75410T=NBRC 110934T).