A new species of Celastraceae, Maytenus megalocarpa, is described and illustrated. The species is known from only a small number of collections from eastern Brazil, in the Atlantic Rainforest of Bahia and Minas Gerais states. It is considered endangered given the rapid deforestation of this biome. The species is readily distinguished from its congeners by its large, tardily dehiscent fruit that does not open by reflexed valves and by the seeds enveloped by thick arils. Given its remarkable fruits and the consequent initial doubt about the generic position of the new species in Celastraceae, a phylogenetic analysis using molecular data from plastid and nuclear rDNA gene regions, together with morphological characters, was performed. The new species was consistently resolved as nested within Maytenus, which itself is paraphyletic. Incongruence between the nuclear and plastid gene regions was identified for Fraunhofera, Maytenus texana, and Plenckia. Future taxonomic changes are necessary to rigorously delimit Maytenus as a natural genus. Additional comments on geographical distribution, phenology and conservation status of the new species are also provided, as well as a key to the species of Neotropical Maytenus with spinoseleaves.