A Gram-stain-negative, non-flagellated, non-gliding, aerobic and rod-shaped bacterium, designated strain OITF-31T, was isolated from a tidal flat in Oido, an island of South Korea, and subjected to a polyphasic taxonomic study. Strain OITF-31T grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 1.0-2.0 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences revealed that strain OITF-31T belonged to the genus Nonlabens, clustering with the type strains of Nonlabens dokdonensis and Nonlabens xylanidelens, sharing 98.1 % sequence similarity with each. Strain OITF-31T exhibited 16S rRNA gene sequence similarities of 93.9-95.8 % to the type strains of other Nonlabens species and less than of 91.8 % to the type strains of other recognized species. Strain OITF-31T contained MK-6 as the predominant menaquinone and iso-C17 : 0 3-OH and iso-C15 : 0 as the major fatty acids. The major polar lipids detected in strain OITF-31T were phosphatidylethanolamine, six unidentified lipids and two unidentified aminolipids. The DNA G+C content of strain OITF-31T was 38.1 mol% and its mean DNA-DNA relatedness values with the type strains of N. dokdonensis and N. xylanidelens were 24 and 19 %, respectively. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain OITF-31T is separated from recognized species of the genus Nonlabens. On the basis of the data presented, strain OITF-31T is considered to represent a novel species of the genus Nonlabens, for which the name Nonlabens aestuariivivens sp. nov. is proposed. The type strain is OITF-31T (=KCTC 52502T=NBRC 112459T).