One of the many taxonomic challenges found in the Dendropsophus microcephalus species group is the Dendropsophus walfordi distinction from D. nanus. Recent phylogenetic inferences have indicated the paraphyly of these species, although they were not designed to assess this issue. To contribute to the delimitation of these species, we analyzed the 12S, 16S and COI mitochondrial genes, the morphological traits, and the advertisement calls of specimens from northern Amazonia to Argentina, including the type localities of D. nanus and D. walfordi. Paraphyly of D. nanus with respect to D. walfordi was inferred by maximum-parsimony and Bayesian analyses, and five major clades exhibiting nonoverlapping geographic distributions were recognized. The bPTP and ABGD analyses supported the existence of five independently evolving lineages in this complex. Acoustic and morphological data clearly distinguished the clade that included the topotypes of D. walfordi from the others, corroborating the validity of this species. To avoid the paraphyly of D. nanus with respect to D. walfordi, we recognize the clade distributed from central-southern Brazil to Argentina as D. nanus, the clade distributed in Amazonia as D. walfordi, and discuss the existence of unnamed cryptic species closely related to D. nanus and D. walfordi.