Ongoing studies of Neotropical Euphorbiaceae have uncovered a surprising number of new species belonging to Croton L. sect. Cleodora (Klotzsch) Baill., one of the better studied clades in the genus. Here we describe six new species and reclassify three others that were either misplaced to section or regarded as species of unknown phylogenetic affinity in previous studies. The new species are all from South America, and five of them are restricted to the Amazon region. We update the most recent taxonomic revision of Croton sect. Cleodora by providing a new taxon list and an identification key for the 27 currently recognized species. Sixteen species occur in lowland forested areas of the Amazon basin. Our finding calls attention to the Neotropics, and the Amazon region in particular, where information about the flora and species geographic ranges is still incomplete, even for relatively well-studied plant groups.