A novel strain, designated J221(T), was isolated from the intestine of a sea cucumber, Apostichopus japonicus, collected from earthen ponds in Qingdao, China. The strain was Gram-negative, oxidase-positive, aerobic, rod-shaped and motile by means of one to several polar flagella. Growth of strain J221(T) was observed at temperatures between 10 and 40 °C with optimum growth between 25 and 28 °C. The pH range for growth was 5.0-9.0 with optimum growth at pH 7.5-8.0. The dominant fatty acids were summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c, 29.04 %), C16 : 0 (28.93 %) and C18 : 1ω7c (26.15 %). The major polar lipids were phosphatidylglycerol and phosphatidylethanolamine. Diphosphatidylglycerol, an unknown aminolipid and an unknown aminophospholipid were present in moderate to minor amounts in the polar lipid profile. Strain J221(T) had Q-8 as the major respiratory quinone. The DNA G+C content of strain J221(T) was 46.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J221(T) is a member of the Gammaproteobacteria. It formed a distinct phyletic line with less than 91 % sequence similarity to any species within previously recognized genera. On the basis of this polyphasic taxonomic study, strain J221(T) should be classified as a representative of a novel species of a new genus, for which the name Neiella marina gen. nov., sp. nov. is proposed. The type strain of Neiella marina is J221(T) ( = CGMCC 1.10130(T) = NRRL B-51319(T)).