A Gram-stain-negative, rod-shaped, non-motile, aerobic and orange-pigmented marine bacterium, designated strain L53T, was isolated from an oyster sample collected from the coast of Weihai, China (122.0° E 37.5° N). Growth of strain L53T occurred at 4-40 °C (optimum, 33 °C), at pH 6.5-8.0 (optimum, pH 7.5) and with 1.0-7.0 % (w/v) NaCl (optimum, 3.0 %). Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain L53T was closely related to Bizionia echini KCTC 22015T (96.9 %) and Hanstruepera neustonica JCM 19743T (96.1 %). Strain L53T was located in a distinct phyletic lineage in a discrete clade associated with H. neustonica JCM 19743T. The DNA G+C content of strain L53T was 33.5 mol%. The sole menaquinone was MK-6. The polar lipids comprised one phosphatidylethanolamine, four unidentified aminolipids and four unidentified lipids. The major fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 0 G. Based on morphological, physiological and molecular properties as well as on phylogenetic distinctiveness, strain L53T should be placed in the genus Hanstruepera as representing a novel species, for which the name Hanstruepera crassostreae sp. nov. is proposed. The type strain is L53T (=KCTC 62247T=MCCC 1H00246T).