A novel bacterial strain, designated MK52T, was isolated from the phycosphere of Microcystis aeruginosa . Strain MK52T is a Gram-stain-negative, pink-pigmented, rod-shaped, strictly aerobic bacterium. In 16S rRNA phylogenetic analysis, the MK52T strain was most closely related to Rhizorhabdus wittichii RW1T (98.66 %) and Rhizorhabdus histidinilytica UM2T (98.51 %). The genomic DNA G+C content of strain MK52T was calculated to be 65.5 mol%. The average nucleotide identity values of strain MK52T with R. wittichii RW1T and R. histidinilytica UM2T were 80.35 and 80.23 %, respectively, with digital DNA–DNA hybridization values of 23.6 and 22.9 %, respectively, and average amino acid identities of 75.59 and 75.79 %, respectively. The major isoprenoid quinone was Q-10, and the predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and sphingoglycolipid. Fatty acid methyl ether analysis showed that summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) was the main cellular fatty acid in strain MK52T. Strain MK52T cells grew at 21–34 °C (optimum, 30 °C), pH 5–8 (optimum, pH 7) and with 0–2 % (w/v) NaCl (optimum, 0.5 % NaCl). Rhizorhabdus phycosphaerae sp. nov. is proposed as a new species (=KCTC 72877T=DSM 111424T) based on its genotypic and phenotypic characteristics.