The generic classification of Neotropical Eumeninae has been termed chaotic, and synonymisation of taxa has become constant in recent years. Recognition of some generic limits are problematic due to features showing a great deal of variation, such as the length of the first metasomal tergum. This applies to the Neotropical Alphamenes van der Vecht, Minixi Giordani Soika and Pachyminixi Giordani Soika. Minixi has already been demonstrated to be paraphyletic in regards to Pachyminixi. These taxa are the focus of the present study, which used morphological data to infer the phylogenetic relationships among their constituent species. A total of 14 taxa and 34 characters were subjected to cladistic analysis under implied weighting. A single most-parsimonious cladogram was obtained, recovering Pachyminixi as monophyletic. Minixi, however, was paraphyletic relative to Pachyminixi and they are thus synonymised, with the former name having priority. A new species from Mexico, Minixi mariachii, sp. nov., is described. Minixi joergenseni bicingulatus (Zavattari, 1912) is synonymised under M. joergenseni (Schrottky, 1909), comb. nov. Additional new combinations are: Minixi arechavaletae (Brèthes, 1903), comb. nov., M. bifasciatum (von Schulthess, 1904), comb. nov., M. brethesi (Bertoni, 1927), comb. nov., M. sumichrasti (de Saussure, 1875), comb. nov., and M. uruguyense (de Saussure, 1855), comb. nov. Illustrations and a new key to species of Minixi are provided. The present study enhances our knowledge on Neotropical potter wasp systematics, providing one further step into a natural classification for a group whose taxonomy has suffered from irrational splitting of genera in the past century.