A total of 139 surface sediment samples, collected from the continental shelf and slope off the southeastern coast of Korea, were analyzed in order to understand their grain-size, mineral composition and organic carbon content. Based on the grain-size characteristics, five surface sedimentary facies were distinguished: sand, clay, mud, sand-mud mixed, and sand-clay mixed facies. The sand facies appears to be composed mostly of relict sand. For mud, most of which seem to be of recent origin, two different sources were suggested, based principally on their areal distribution pattern and the local hydrographic conditions. Heavy mineral composition of the fine-sand size fraction allowed us to distinguish different sand populations from the study area. On the whole, the Hupo Bank sediments showed a high content of garnet, while the sediments from the northern part of the continental shelf were characterized by a relatively high content of metamorphic minerals (kyanite, sillimanite, andalusite, staurolite). Among clay minerals, the most abundant was illite, with chlorite, kaolinite and smectite following in decreasing order. Organic carbon contents in the sediments of the study area were generally high and showed an average value of 1.94%. The sediment grain-size exerted a strong influence on the organic carbon content. The highest organic carbon content, on the other hand, was found in the continental slope sediments.