A Gram-stain-negative, oval- or short-rod-shaped and non-motile bacterial strain, designated KEM-3T, was isolated from water of Geumgang Estuary Bank, South Korea, and was subjected to a polyphasic taxonomic study. Strain KEM-3T grew optimally at pH 7.0-8.0, at 25 °C and in the presence of 2-3% (w/v) NaCl. The neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain KEM-3T fell within the clade comprising Altererythrobacter species, clustering with Altererythrobacter confluentis KEM-4T and Altererythrobacter gangjinensis KJ7T, with which it exhibited 97.3 and 96.0 % sequence similarity, respectively. The 16S rRNA gene sequence similarity values between strain KEM-3T and the type strains of other Altererythrobacter species were 92.9-95.2 %. The DNA G+C content of strain KEM-3T was determined to be 59.0 mol% and its mean DNA-DNA relatedness with A. confluentis KEM-4T was 8.6±3.1 %. Strain KEM-3T contained Q-10 as the predominant ubiquinone and summed feature 8 (C18:1ω7c and/or C18:1ω6c), C17:1ω6c and summed feature 3 (C16:1ω6c and/or C16:1ω7c) as the major fatty acids. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, a sphingoglycolipid, an unidentified glycolipid and an unidentified phospholipid. Differential phenotypic properties, together with phylogenetic distinctiveness, demonstrated that strain KEM-3T is distinguishable from other Altererythrobacter species. On the basis of the data presented, strain KEM-3T is considered to represent a novel species of the genus Altererythrobacter, for which the name Altererythrobacter aquiaggeris sp. nov. is proposed. The type strain is KEM-3T (=KCTC 52471T=NBRC 112425T).