BackgroundIctalurusis one of the most representative groups of North American freshwater fishes. Although this group has a well-studied fossil record and has been the subject of several morphological and molecular phylogenetic studies, incomplete taxonomic sampling and insufficient taxonomic studies have produced a rather complex classification, along with intricate patterns of evolutionary history in the genus that are considered unresolved and remain under debate.ResultsBased on four loci and the most comprehensive taxonomic sampling analyzed to date, including currently recognized species, previously synonymized species, undescribed taxa, and poorly studied populations, this study produced a resolved phylogenetic framework that provided plausible species delimitation and an evolutionary time framework for the genusIctalurus.ConclusionsOur phylogenetic hypothesis revealed thatIctaluruscomprises at least 13 evolutionary units, partially corroborating the current classification and identifying populations that emerge as putative undescribed taxa. The divergence times of the species indicate that the diversification ofIctalurusdates to the early Oligocene, confirming its status as one of the oldest genera within the family Ictaluridae.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12862-023-02134-w.