A revised assessment of Croton L. sect. Geiseleria (A. Gray) Baill. is provided. The section as now circumscribed includes 84 species ranging across warm areas of the Americas. A nuclear ITS phylogeny of 150 accessions from 83 species and a chloroplast trnL-F phylogeny of 89 accessions from 65 species were generated to confirm correct phylogenetic placement of the species and to determine if any species previously included in the section should now be excluded. Seven new species are described, and we present a taxonomic synopsis that lists all currently accepted species along with their synonyms, distributions, and pertinent comments. We also recognize four subsections within Croton sect. Geiseleria and list their corresponding species. Based on both morphological and molecular criteria, we now recognize C. lagunillae Croizat as a distinct species, rather than as a variety of C. guildingii Griseb. (now treated as C. suavis Kunth), and we treat C. ramillatus Croizat var. magniglandulifer V. W. Steinm. as a species, C. magniglandulifer (V. W. Steinm.) B. W. van Ee. We also exclude C. tetradenius Baill. from Croton sect. Geiseleria (A. Gray) Baill. along with related species such as C. pulegiodorus Baill. and C. leptobotryus Müll. Arg., which are either members of Croton sect. Adenophylli Griseb. or else may merit new sectional status. We also exclude C. waltherioides Urb., although it is not clear to which section of Croton it belongs.