A novel Gram-stain-negative, rod-shaped, aerobic, oxidase-positive and catalase-positive bacterium of the genus Pseudooceanicola , designated strain E2-1^T, was isolated from surface water of Jiulong River Estuary, PR China. Cells of strain E2-1^T grew in medium containing 0.5–12 % NaCl (w/v; optimum, 2–4 %), at 15–45 °C (optimum, 28–33 °C) and at pH 7.0–9.0 (optimum, pH 7.0–8.0). Comparative analyses of the 16S rRNA gene sequence revealed that strain E2-1^T had the highest similarity to Pseudooceanicola nitratireducens JLT1210^T (97.3 %) and Pseudooceanicola batsensis HTCC2597^T (97.1 %), and had less than 97.0 % 16S rRNA gene sequence similarity to other type strains within the genus Pseudooceanicola . The DNA G+C content of strain E2-1^T was 65.7 mol%. The average nucleotide identity and digital DNA–DNA hybridization relatedness values between E2-1^T and related type strains were 75.0 and 20.1 % with P. nitratireducens JLT1210^T and 75.6 and 20.4 % with P. batsensis HTCC2597^T, respectively. The sole isoprenoid quinone was Q-10; the predominant polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, three unidentified phospholipids and six unidentified lipids; the major cellular fatty acids were C_{16 : 0} (17.5 %), C_{19 : 0} cyclo ω8c (22.7 %) and summed feature 8 (C_{18 : 1} ω7c/C_{18 : 1} ω6c; 10.1 %). According to the phylogenetic and genotypic results, strain E2-1^T represents a novel species in the genus Pseudooceanicola , for which the name Pseudooceanicola aestuarii sp. nov. is proposed. The type strain is E2-1^T (=MCCC 1K03742^T=KCTC 72107^T).