The karyotypes of Neotropical Pseudomyrmecinae were analyzed for the first time. Seven species belonging to the Pseudomyrmex genus from four Brazilian localities had their chromosome number and morphology studied. Six of the nine species groups of Pseudomyrmex were sampled. Chromosome numbers ranged from 2n=24 to 2n=70, characterized in acrocentrics and metacentrics. Our cytogenetic studies indicate that, as in other ants, karyoptype evolution in Pseudomyrmex may have evolved increasing chromosome number and diversifying chromosome morphology, minimizing genetics risks for deleterious mutations through centric fission and pericentric inversion. Such a karyotypic diversity is also recognized in other ants’ subfamilies, especially Myrmeciinae, Ponerinae and Myrmicinae. These first cytogenetic studies in the genus Pseudomyrmex should contribute with other data to the evolutionary history of the Pseudomyrmecinae subfamily.