A systematic revision of the genus Dichaea (Orchidaceae) in Costa Rica is presented. The taxonomic history of the genus and its phylogenetic position are discussed, with emphasis on infrageneric grouping. Characters of vegetative and floral morphology are treated, and their taxonomic significance is discussed. Twenty-nine Dichaea taxa are recognized for the flora of Costa Rica, and a key to species is provided. Each taxon is described on the basis of Costa Rican material, illustrated in a composite plate, and its distribution in the country is assessed. Distribution maps for all the taxa are given. Overall distribution, derivation of name, notes on species ecology, and diagnostic features are presented for each taxon. Lectotypes are selected for D. acostae Schltr., D. acroblephara Schltr., D. amparoana Schltr., D. costaricensis Schltr., D. dammeriana Kraenzl., D. lycopodioides Rchb.f. ex Kraenzl., D. poicillantha Schltr., D. selaginella Schltr., D. tuerckheimii Schltr., Epidendrum echinocarpon Sw., and E. trichocarpon Sw. A new species, D. gomezlauritoi, is described and illustrated from the wet Caribbean plains of central Costa Rica.