Abstract A new species, Alagoasa aurora, from high elevation Costa Rica is described. Adult habitus (dorsal and ventral), mouthparts, and male and female genitalia are illustrated. Morphometric data are presented and graphed. Alagoasa aurora bears a hind tarsomere similar to species of Asphaera, the highly vaulted habitus of Alagoasa, and the large eyes and nocturnal habits usual in Walterianella. This species also bears a mandibular mola that has never been reported before for an oedionychine flea beetle. Phylogenetic affinities and other close relatives of this species are discussed.