Genarchella parva Travassos, Artigas & Pereira, 1928 has been reported mainly in Characidae hosts. The morphology of this species has been known based on specimens collected mainly by Travassos and researchers (20s and 60s decades) and also from specimens in Argentina. The goal of this study was to describe the morphology of G. parva, provide the parameters of the infections from different fish species and discuss the host’s checklist from Brazil. Specimens of G. parva were collected from species of Astyanax Baird & Girard, 1854 and Psalidodon Eigenmann, 1911 in Jacuí Delta (north of the Lake Guaíba, in the municipality of Porto Alegre) and Lagoon Itapeva (municipality of Terra de Areia), extreme south of Brazil. The localization of the genital pore of G. parva and Genarchella fragilis Lunaschi, 1990 was compared and discussed. The prevalence of G. parva was higher in Psalido...