As a result of a taxonomic and phylogenetic study of Chamaecrista sect. Absus, we identified two new species of Chamaecrista from Brazil and Bolivia, which we designate here as C. oppositifolia and C. longistyla. Morphologically, C. oppositifolia resembles C. sincorana, while C. longistyla is similar to C. paraunana and C. brevicalyx. Description, illustration, diagnostic morphology, systematic position, phenology, distribution, images and preliminary conservation status are provided for both new species. Phylogenetic inference and morphology show that the two new species are clearly distinct and belong to C. sect. Absus, ser. Rigidulae (C. oppositifolia) and ser. Absoideae (C. longistyla).