The hitherto unknown female of Napaea joinvilea Hall & Harvey, 2005 (Lepidoptera: Riodinidae: Mesosemiini) is described, and new distribution records for the species—until now only known from a single locality in the state of Santa Catarina, Brazil—are presented, expanding the distribution more than 1.500 kilometers northwards. Diagnosis and description of the female, distinction from similar sympatric species, illustrations of the imagines and male and female genitalia are provided. Special attention is given to distinguish N. joinvilea from its sisterspecies, N. melampia (Bates, 1867), a rare species known only from unspecified localities in the state of Bahia, Brazil. Based on the female and the new distributional records, N. joinviliea is clearly recognized as a distinct species.