A Gram-stain-negative, strictly aerobic and moderately halophilic bacterium, designated strain AsT0115T, was isolated from a red marine alga, Asparagopsis taxiformis. Cells were non-motile rods showing oxidase-positive and catalase-negative activities. Growth was observed at 15-37 C (optimum, 25 C) and pH 6.5-7.5 (optimum, pH 7.0) and in the presence of 0-11.0% (w/v) NaCl (optimum, 2.0-3.0%). Strain AsT0115T contained iso-C15:0 and iso-C15:1 G as the predominant fatty acids. Menaquinone-6 was identified as the sole isoprenoid quinone. Major polar lipids consisted of phosphatidylethanolamine, an identified aminolipid and three unidentified polar lipids. The G+C content of the genomic DNA calculated from the whole genome sequence was 41.7 mol%. Strain AsT0115T was most closely related to Flagellimonas pacifica sw169T and Flagellimonas flava DSM 22638T with 96.5% and 95.6% 16S rRNA gene sequence similarities, respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AsT0115T formed a phyletic lineage with F. pacifica sw169T within the genus Flagellimonas. Phenotypic, chemotaxonomic, and phylogenetic features clearly suggested that strain AsT0115T represents a novel species of the genus Flagellimonas, for which the name Flagellimonas algicola sp. nov. is proposed. The type strain is AsT0115T (= KACC 19790T = JCM 32942T).