A Gram-staining-negative, strictly aerobic and rod-shaped bacterium, designated strain CNURIC013(T), was isolated from seawater collected on the coast of Jeju Island, South Korea. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain CNURIC013(T) belonged to the genus Tenacibaculum, within the family Flavobacteriaceae. Sequence similarities between the novel strain and the type strains of recognized species of the genus Tenacibaculum were 93.6-96.0 %, the highest value being with Tenacibaculum litopenaei B-I(T) (96 %). The DNA G+C content of the novel strain was 34.5 mol% and the major respiratory quinone was menaquinone-6. The major fatty acids were summed feature 3 (comprising C(16 : 1)ω7c and/or iso-C(15 : 0) 2-OH; 26.0 %), iso-C(15 : 0) (24.4 %), iso-C(15 : 1) G (18.5 %) and iso-C(17 : 0) 3-OH (8.1 %). The polar lipids consisted of phosphatidylethanolamine, one unknown aminophospholipid and nine unknown polar lipids. On the basis of the phenotypic, phylogenetic and genotypic data, strain CNURIC013(T) represents a novel species within the genus Tenacibaculum, for which the name Tenacibaculum jejuense sp. nov. is proposed. The type strain is CNURIC013(T) ( = KCTC 22618(T) = JCM 15975(T)).