The diet of Patagonian toothfish (Dissostichus eleginoides) was investigated in two offshore regions in the southwestern Atlantic: on the Argentinian continental shelf/slope between 46°-55°S and 60°-64°W, and around South Georgia between 53°-55°30' and 3°-45°W. The South Georgia area was divided into two zones: the shelf zone and deep-water zone. On the Argentinian continental shelf/slope, the length of D. eleginoides ranged from 30 to 95 cm total length (TL) which corresponds to the juvenile stage. Around South Georgia, the size distribution included both juvenile and adult stages, and ranged between 18 and 212 cm TL. The diets of fish of various sizes and both sexes were compared, and the feeding status of this species is discussed. D. eleginoides is a mixed-species carnivore, feeding principally on fish and secondarily on crustaceans and cephalopods. The principal fish species in the diet of D. eleginoides on the Argentinian continental shelf were nototheniids (e.g. Patagonotothen ramsayi). Around South Georgia, adult D. eleginoides preyed mainly on fish (Zoarcidae, Moridae, Bathydraconidae, Channichthyidae) and on Decapoda, while juveniles in coastal waters consumed krill and, in deeper waters, various species of fish (Nototheniidae, Myctopliidae, Channichthyidae). It was also found that the diet of D. eleginoides varied in relation to its size and water depth in both the shallow and deep-water zones.