Based on herbarium specimens and recent collections made in the last few years, we have found 19 species that are for the first time recorded for Bolivia (9 species) and/or Brazil (12 species). Full specimen citations, comments about previously known distributions, and taxonomic notes are presented for all species. In Bolivia, all new records are for species of Adiantum, mostly from lowland regions in northern and eastern Bolivia. In Brazil, most of the new records are for Amazonian Brazil, near the boundaries with neighboring countries. One record is for southern Bahia, showing a clear disjunction between Venezuelan-Guayanan Shield and the Serra do Mar Mountains in northeastern Brazil.