Recent sampling on fish from the headwaters of the Jordão and Areia rivers, combined with collection databases and specialized literature reports, yielded the first species inventory. Both basins reflect the high endemism rate associated with the Iguaçu River. However, four species previously thought to be restricted to the Jordão River basin are now known to also occur in the basin of the Areia River: Astyanax jordanensis Vera Alcaraz, Pavanelli & Bertaco, 2009; Characidiumtravassosi Melo, Buckup & Oyakawa, 2016; Jenynsia diphyes Lucinda, Ghedotti & Graça, 2006; and Trichomycterus igobi Wosiacki & de Pinna, 2008. This suggests an ancestral connection between the tributaries of the Jordão and Areia rivers, with putative drainage rearrangements resulting from the uplift of the Serra da Esperança. The endemic fauna of this region is presently threatened by invasive species, the construction of dams, and other human activities.