This work provides the first information about the stomach contents of juvenile green turtles (Chelonia mydas) on the coast of Rio de Janeiro State, south-eastern Brazil (22°50′S–23°00′S). Between June 2009 and May 2010, we obtained 49 stomach contents of specimens that were stranded, of which 37 contained food items. Among food items, macroalgae stood out with 83.7% frequency of occurrence in the stomachs analysed and 37 species were identified. The most representative macroalgae in the stomach contents were: Sargassum vulgare, Ulva lactuca, Gelidiella acerosa and Pterocladiella capillacea. Teleosts and molluscs were also recorded in the stomach contents of the species in the region; however, with low representativeness. Analysis of stomach contents confirmed herbivory as the preferred dietary pattern of C. mydas.