Long-term variability in the coastal sea surface temperature (SST) in Korea was investigated to examine the earlier results in depth by analyzing the coastal SST time series extending to recent years. There is a common tendency of the interannual variability with period of 3-5 year at most of the stations. Though a long term linear increasing trend is remarkable with the rate over 0.02°C/year at almost all the stations, it is also noticeable that SST is lower in the 1970s and early 1980s but higher in the 1990s and early 2000s after the increase in the late 1980s. The pattern of the interannual variability of SST is similar to that of air temperature.The increasing trend of minimum SST in winter is obvious at most stations, but the linear trend of maximum SST in summer is less definite. Therefore, the decreasing tendency of annual amplitude is mainly due to the increasing tendency of SST in winter.