A Gram stain-negative, aerobic, motile, rod-shaped bacterial strain, designated CAU 1509T, was isolated from marine sediment, and its taxonomic position was determined using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CAU 1509T formed a distinct lineage within the genus Sinimarinibacterium with the highest 16S rRNA gene sequence similarity to Sinimarinibacterium flocculans NH6-24T (97.0%). Similar to another member of Sinimarinibacterium, ubiquinone-8 (Q-8) was the predominant quinone, whereas C16:0, summed feature 3 (C16:1ω7c/ω6c) and summed feature 8 (C18:1ω7c/ω6c) were the major cellular fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid, four unidentified glycolipids and three unidentified aminolipids. Strain CAU 1509T has a genome of 4.54 Mb, including 4251 coding sequences, 6 rRNAs and 50 tRNAs, with a genomic DNA G+C content of 63.2 mol%. Based on its phenotypic, chemotaxonomic and phylogenetic properties, strain CAU 1509T should be classified as a novel species of the genus Sinimarinibacterium, for which the name Sinimarinibacterium arenosum sp. nov. is proposed. The type strain is CAU 1509T (= KCTC 72000T = NBRC 113698T).