A concept of the higher-level phylogeny of the Eumeninae remains elusive. As such, the naturalness of several genera occurring in the Neotropical region is doubtful, including Monobia and Montezumia. Morphological data were used to infer the phylogenetic relationships among the species groups within both genera, as well as to test their monophyly. Analyses recovered Monobia and Montezumia as monophyletic as long as Montezumia arizonensis and Montezumia aurata were included in Monobia. Most species groups proposed by Willink in 1982 were also recovered as monophyletic. Three new combinations are proposed in congruence with the phylogenetic results: Monobia arizonensis, new combination, Monobia aurata, revised combination, and Monobia oaxaca, new combination. An additional new species is described: Monobia goiana Hermes, new species.