A Gram-stain negative, strictly aerobic, chemoheterotrophic, tangerine orange pigmented, curved-rod shaped bacterium, designated N5DA8-2C(T), was isolated from a sea squirt by use of a bait-streaked agar technique. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the novel marine strain is affiliated with the family Flavobacteriaceae of the phylum Bacteroidetes and that it shared high (92.6 %) sequence similarity with Frondibacter aureus A5Q-67(T). The strain could be differentiated phenotypically from the related members of the family Flavobacteriaceae. The major fatty acids of strain N5DA8-2C(T) were iso-C15:1 G, iso-C17:0 3-OH, iso-C15:0 and C16:1 ω7c and/or C16:1 ω6c. A polar lipid profile was present consisting of phosphatidylethanolamine and three unidentified amino lipids. The DNA G+C content of the strain was determined to be 41 mol% and the major respiratory quinone was identified as menaquinone 6 (MK-6). From the distinct phylogenetic position and combination of genotypic and phenotypic characteristics, the strain is considered to represent a novel genus in the family Flavobacteriaceae, for which the name Ascidiimonas aurantiaca gen. nov., sp. nov. is proposed. The type strain of A. aurantiaca gen. nov., sp. nov. is N5DA8-2C(T) (= KCTC 32992(T) = NBRC 110020(T)).