Atractus carrioni was described based on two specimens from Loja, in the western versant of Cordillera Real, Ecuador. Posteriorly, 13 additional individuals were reported in the literature, but this entire sample was obtained in the neighborhood of Loja, and indeed comprises topotypes of A. carrioni. Thus, despite the fact that we are acquainted with some aspects of the intra-populational variability of the species (few merestic and morphometric features), nothing is known about its ontogenetic, sexual and geographical variation, as well as its natural history. During the examination of Ecuadorian and Peruvian collections, we found 28 additional specimens of this poorly known snake. In this paper, we report new localities and data on meristic, morphometric, color pattern, and hemipenis variation for the species. We associate the variation displayed by these character systems with sexual, geographic, and ontogenetic phenomena. We provide detailed comparisons of the former taxon with their putative closely related species (A. roulei), and propose a new species group to accommodate A. carrioni and A. roulei. Additionally, we provided the first data on reproduction for Andean species of Atractus.