The stocks of Antarctic toothfish, Dissostichus mawsoni were a relatively economically and ecologically important fishery resource in the waters of Antarctic. However, there is not enough data and information to assess the robust stocks and deliberate proper measurements for sustainable utilize, especially relate to diet and feeding strategy which may lead to think about ecosystem based stock assessments and fishery managements. Therefore, the Korean scientists analyze diet composition and feeding strategy of D. mawsoni in the research blocks 58.4.2-1, 58.4.1-2, 58.4.1-3, 58.4.1-4, and 58.4.1-5 as a part of Korean research plan for the exploratory longline fishery for Dissostichus spp. during 2014/2015 season. This study was carried out based on the results of stomach content identification of the D. mawsoni caught in the research blocks 58.4.2-1, 58.4.1-2, 58.4.1-3, 58.4.1-4, and 58.4.1-5 in CCAMLR Conversion Area from December 2014 to March 2015. The diet composition and feeding strategy of D. mawsoni were studied using 549 specimens (74 to 181 cm in body length). D. mawsoni is a carnivore and piscivorous fish that mainly consumed fishes, especially Macrourus spp. with 47.6% of the diet by weight. Its diet also included small quantities of crustaceans, mollusks, and birds. In this study, fishes were the dominant prey item in all size classes (<100 cm (74-100 cm), n = 6; 100-120 cm, n = 31; 120-140 cm, n = 148; 140-160 cm, n = 221; 160 cm< (160-181 cm), n = 43). In the fish prey items, macrouidae were the dominant prey item in three size classes (120-140 cm, 140-160 cm, and 160 cm< (160-181 cm) The graphical method for feeding strategy revealed that D. mawsoni is an opportunistic and specialized predator on fishes and macrouidae, and showed narrow niche width.