A marine actinomycete strain, designated KSW2-15(T), was isolated from a dried seaweed sample collected from a sandy beach on the coast of Jeju in the Republic of Korea. The organism produced non-motile, non-endospore-forming, Gram-positive, coccoid cells. The colonies were circular, translucent and yellow in colour with entire margins. meso-Diaminopimelic acid was present as the diamino acid of the peptidoglycan. The acyl type of the muramic acid was acetyl. Mycolic acids were not present. The predominant menaquinone was MK-8(H(4)). The polar lipids were phosphatidylethanolamine, phosphatidylinositol and diphosphatidylglycerol. The major cellular fatty acids were of the saturated, unsaturated and iso-branched methyl types. The DNA G+C content was 74 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain KSW2-15(T) formed a loose association with 'Candidatus Nostocoida limicola', within the radiation of the family Intrasporangiaceae of the suborder Micrococcineae. The organism showed the highest levels of sequence similarity with 'Candidatus Nostocoida limicola' (96.1 %), Terrabacter tumescens (96.1 %) and Terrabacter terrae (96.0 %). The levels of 16S rRNA gene sequence similarity between the isolate and members of other genera of the family Intrasporangiaceae were in the range 92.1-95.5 %. On the basis of the polyphasic evidence, the isolate should be classified within a novel genus and species, for which the name Phycicoccus jejuensis gen. nov., sp. nov. is proposed. The type strain of Phycicoccus jejuensis is strain KSW2-15(T) (=KCCM 42315(T)=NRRL B-24460(T)).