A new species of Oxalis sect. Holophyllum restricted to the Atlantic Forest of the State of Espírito Santo (Brazil) is described. This species can be distinguished from others of the section by the leaf blades up to ca. 1.6× longer than wide, adaxially with very abundant, patent hairs, phyllodial peduncles shorter than the leaves, distally enlarged and hiding floral buds and young fruits underneath, and flowers with yellow corolla. A morphological description with taxonomic notes and a preliminary assessment of its conservation status are presented here, as well as a photographic plate, and a geographic distribution map for the new species. An identification key for the species of O. sect. Holophyllum with the peduncle wider distally than proximally is also provided.