The morphology and infraciliature of a new marine ciliate, Tachysoma multinucleata sp. nov., collected from the Jawol Island near Incheon, Korea, were investigated using live observation and protargol impregnation. The new species is characterized by: size in vivo about 65×25 μm, body oval to ellipsoid. Three frontal, one buccal, four frontoventral, three ventral and two pretransverse cirri. Fifteen to 22 left and 13–21 right marginal cirri and about 21–27 adoral membranelles. Cortical granules fine and yellowish, arranged around cirri and dorsal cilia. Usually 12–26 macronuclear nodules. Three dorsal kineties. Marine habitat.