This paper presents data on the incidental catch of sea turtles in both the Brazilian exclusive economic zone and adjacent international waters (both areas are located mainly in the south-western Atlantic) by Brazilian commercial pelagic longliners targeting swordfish, tuna and sharks. Data were obtained by on-board observers for 311 trips carried out in 2001–2005, totalling 7385 sets and 11,348,069 hooks. A total of 1386 sea turtles were incidentally captured in the five years (some of them were considered dead at capture): 789 loggerheads (Caretta caretta), 341 leatherbacks (Dermochelys coriacea), 45 green turtles (Chelonia mydas), 81 olive ridleys (Lepidochelys olivacea) and 130 of unknown species. Taking into account the distribution of the fishing effort in the study area and the incidental catch of sea turtles, four regions were highlighted for the analyses: Zone 1 is located off the northern Brazilian coast; Zone 2 is located off the central Brazilian coast; Zone 3 is the region off the southern Brazilian coast; and Zone 4, located in the open sea almost totally within international waters, is the region around a chain of undersea mountains known as the Rio Grande Rise (Elevação do Rio Grande). There is no information on the origin (nesting areas) of the captured olive ridleys, but there is some evidence, obtained through genetic and demographic analyses, that loggerheads, leatherbacks and green turtles inhabiting the open ocean around Brazil originate from nesting areas in several countries. Together with the fact that the south-western Atlantic is fished by longliners again from several countries, this places the conservation of sea turtles in that part of the ocean in an international context. Some conservation actions carried out by Brazil concerning the interaction between pelagic longlines and sea turtles in the study area are described.