A new species of the genus Senna from the Atlantic Forest of Paraíba State, Brazil, is described and illustrated based on a field collection, traditional taxonomic methodologies, and the analysis of Senna collections at RB and the main herbaria in northeastern Brazil. Morphologically, Senna pluribracteata is related to a group of four species of Senna sect. Chamaefistula ser. Bacillares: S. macranthera, S. pinheiroi, S. rizzinii, and S. rugosa, although S. pluribracteata has a set of distinctive anatomical characters that differentiate it: two extrafloral nectaries between leaflets in the rachis; large and conspicuous elliptic bracts 7.0–9.0 mm long along the inflorescence peduncle; the epidermis on the abaxial surface is conspicuously and compactly papillose; the rounded leaflet margins have palisade parenchyma near the apex; the mesophyll is dorsiventral with a single layer of palisade parenchyma, with isodiametric cells occupying approximately 60% of that structure; the petiole has a somewhat pentagonal shape and is planar adaxially; the rachis is obdeltoid and planar adaxially. Morphological and leaf anatomical descriptions, and a key to identifying the seven species of Senna ser. Bacillares found in Paraíba State are provided. The morphological and anatomical affinities of S. pluribracteata and its allied taxa are discussed.