An aerobic, gram-negative, yellow-pigmented, and non-motile bacterium designated KMM 9535T was isolated from a marine sediment sample obtained from the Sea of Japan seashore and subjected to a phylogenetic and phenotypic study. On the basis of 16S rRNA gene sequence analysis, strain KMM 9535T was placed to the genus Flavobacterium sharing the highest sequence similarities to Flavobacterium ahnfeltiae KCTC 32467T (99.3 %), Flavobacterium jumunjinense KCTC 23618T (96.5 %), Flavobacterium ponti KCTC 22802T (96.3 %), Flavobacterium urocaniciphilum JCM 19142T (96.1 %), and Flavobacterium gelidilacus LMG 21477T (95.8 %). The DNA–DNA hybridization value between strain KMM 9535T and the closest related F. ahnfeltiae KCTC 32467T was 33 %. Strain KMM 9535T grew at 5–36 °C and in the presence of 0–3 % (w/v) NaCl. It contained MK-6 as the predominant menaquinone, and the major fatty acids were iso-C15:0, iso-C17:1, iso-C15:1, and iso-C17:0 3-OH. The DNA G+C content was 28.8 mol%. On the basis of the results obtained, it is proposed strain KMM 9535T to be classified as a novel species of the genus Flavobacterium, Flavobacterium maris sp. nov., with the type strain of the species KMM 9535T (=NRIC 0920T = KCTC 42093T).