The azooxanthellate soft coral Dendronephthya suensoni (Holem, 1895) is distributed mainly around Jejudo Island, Korea. This species was determined as gonochoric with a sex ratio of 2:1 (female:male). Both female and male colonies have one gametogenic cycle a year. The annual reproductive cycle of D. suensoni is dependent on the seawater temperature. In particular, reproduction of the male colony showed a higher positive correlation between seawater temperature and the mean diameter of the spermaries. Gametogenesis in females and males took 6 months and 12 months, respectively. The mean diameter of a mature oocyte was $249.29;{pm};36.24;{mu}m$, with a maximum size of $354.45;{mu}m$. Spawning could have occurred in the fall after the seawater temperature began to decrease.