ABSTRACT: Characterizing the behaviors of sea turtles and identifying high-use areas as they vary in time and space is important for conservation planning, particularly when turtles overlap with fisheries that may unintentionally harm them. Between July 2006 and March 2010, 27 satellite transmitters were deployed at sea on juvenile loggerheads Caretta caretta captured as bycatch in the Uruguayan and Brazilian pelagic longline fisheries operating in the Southwestern Atlantic Ocean. Tracking duration ranged from 3 to 639 d (mean ± SD: 259 ± 159 d; n = 27), during which turtles moved between latitudes of 25 to 45°S and longitudes 35 to 54° W. High-use areas for the tracked turtles were over the continental shelf and slope within the Uruguayan, Argentinian, and Brazilian exclusive economic zones and in adjacent international waters. Diving information was available for 5 turtles. The maximum dive depth recorded varied between 100 and 300 m. Two turtles demonstrated potential bottom-feeding behaviors by diving to depths that corresponded closely with the depth of the seafloor (<200 m) at their given location. The sea surface temperature encountered by tagged turtles was on average 19.8 ± 2.3°C (range: 10.2 to 28.4°C), and turtles showed an affinity for waters supporting moderate to high primary productivity levels (0.43 ± 0.89 mg m^-3 chlorophyll a). Latitudinal movements varied by season and sea surface temperature. These findings, along with those of other studies conducted in the region, demonstrate the need to strengthen ongoing collaborative efforts between neighboring countries and other international partnerships to further the research and management of sea turtles in this area.