Two Gram-stain-negative, facultative anaerobic, rod-shaped and non-gliding bacteria, designated as HL-DH10T and HL-DH14, were isolated from the halophyte Suaeda japonica in a mudflat, Republic of Korea. Based on the results of 16S rRNA gene pairwise analysis, the two isolates were the members of the family Flavobacteriaceae, and Aestuariibaculum suncheonense SC17T was the most closely related to strains HL-DH10T and HL-DH14 with 96.3% and 95.4% sequence similarity, respectively. The average nt identity and digital DNA–DNA hybridization values between strains HL-DH10T and HL-DH14 and other related species were all less than 79.2% and 21.9%, respectively. The genomic DNA G+C contents of strains HL-DH10T and HL-DH14 were 32.0% and 31.5%, respectively. Cells of these strains showed optimal growth at 25 °C, pH 6.5–7.0 and 2.5–4.0% (w/v) sea salts. The major respiratory quinone was menaquinone-6. The major cellular fatty acids were iso-C15:0 (14.0–16.0%), iso-C15:1 G (10.0–12.0%), iso-C17:0 3-OH (12.4–13.9%), iso-C15:0 3-OH (11.8–14.9%) and anteiso-C15:0 (9.4–10.6%). The polar lipids consisted of phosphatidylethanolamine, an unidentified aminophospholipid, two to three unidentified aminolipids and three unidentified lipids. The comprehensive phylogenetic, genomic, phenotypic and chemotaxonomic results indicate that strains HL-DH10T and HL-DH14 are considered to represent a novel genus of Flavobacteriaceae. Hence, we propose the novel genus Thalassobellus suaedae gen. nov., sp. nov. The type strain is HL-DH10T (=KCCM 90512T=JCM 36598T).