Two new Brazilian species of Machaerium Pers. sect. Oblonga (Benth.) Taub. (Leguminosae) are described and illustrated. Machaerium macaense C. V. Mendonça, A. M. G. Azevedo & H. C. Lima is a tree species endemic to the Reserva Ecológica Macaé de Cima, an area of Atlantic forest in Rio de Janeiro State, Brazil. The species is closely similar to M. nyctitans (Vell.) Benth., from which it differs by its smooth bark, smaller leaflets, sunken secondary veins, narrower bracteoles, and smaller standard petal. It is also similar to M. hatschbachii Rudd, from which it differs by bark characters, the bracteoles that are shorter than the calyx, and its inconspicuous stigma. The second new species, M. jobimianum C. V. Mendonça & A. M. G. Azevedo, has a wider distribution than the first, in Minas Gerais, Espírito Santo, and Bahia states, occurring in Atlantic and mesophitic forests or as a pioneer in secondary vegetation. Its habit is a shrub, and it has been confused with M. floridum (Mart. ex Benth.) Ducke, from which it differs by its lustrous and glabrous leaflets, ovate bracteoles, and glabrous stamens. The species is also closely similar to M. myrianthum Spruce ex Benth., a vine or shrub from the Amazon Basin, which has wider paniculate inflorescences, a pandurate standard, and a longer stipe.