The genus Xylodonta Becker (Notodontidae, Nystaleinae) is reviewed for Costa Rica based on 1,571 reared and wild-collected specimens. Eleven species are recorded, of which six are newly described: Xylodonta markvanputteni Chacón, Xylodonta patrickgoodwilliei Chacón, Xylodonta scottmilleri Chacón, Xylodonta andrewrusselli Chacón, Xylodonta robertodelgadoi Chacón, and Xylodonta billhaberi Chacón. Xylodonta terrena (Schaus, 1892) and Xylodonta xylinata (Walker, 1865) are redescribed and Xylodonta angustipennis (Schaus, 1911), Xylodonta rufitincta (Dyar, 1913), and Xylodonta guarana (Schaus, 1892) are discussed. Adults and genitalia are illustrated. Species are described and diagnosed through their distinctive COI barcodes, genital morphology and life histories. Xylodonta adults and caterpillars, and their foodplants in Área de Conservación Guanacaste (ACG) in northwestern Costa Rica, are reviewed. Larvae of four species are illustrated.