A Gram-positive, non-motile, aerobic, coccus-shaped bacterium, designated strain LNB-140T, was isolated from a sewage treatment plant in the Republic of Korea and was characterised using a polyphasic taxonomic approach. Comparative 16S rRNA gene sequence analysis showed that strain LNB-140T belongs to genus Tessaracoccus in the family Propionibacteriaceae of the phylum Actinobacteria. The 16S rRNA gene sequence similarities between strain LNB-140T and type strains of the genus, Tessaracoccus flavescens SST-39T and Tessaracoccus rhinocerotis YIM101269T are 97.8 and 97.4 %, respectively. The chemotaxonomic properties of strain LNB-140T are consistent with those of members of the genus Tessaracoccus: a quinone system with MK-9(H4) as the predominant menaquinone; anteiso-C15:0 and iso C15:0 as the predominant cellular fatty acids; and ll-2,6-diaminopimelic acid as the diagnostic peptidoglycan diamino acid. The major polar lipids were identified as diphosphatidylglycerol and phosphatidylethanolamine. The G+C content of the genomic DNA was determined to be 67.1 mol%. Differential phenotypic properties along with low DNA–DNA relatedness (<30 ± 3.2 %) with closely related type strains show that strain LNB-140T is distinct from previously described members of the genus Tessaracoccus and represents a novel species in this genus, for which the name Tessaracoccus defluvii sp. nov. is proposed. The type strain is LNB-140T (=KEMB 5401-076T = JCM 17540T).