Thirty-one taxa of Gyalideopsis and its recent segregates (Ferraroa, Jamesiella, Lithogyalideopsis) are reported in a first assessment of the group from Costa Rica. Six species are described as new, all originating from perhumid montane rainforest: Gyalideopsis altamirensis Lücking & Umaña, with broadly sessile, brown apothecia and single-spored asci with muriform ascospores (hyphophores unknown); G. macarthurii Lücking, Umaña & Aptroot, with dark greyish brown apothecia having their margin covered by triangular thalline lobules and shortly bristle-shaped hyphophores producing moniliform diahyphae; G. pseudoactinoplaca Lücking & Chaves, with sessile, globose diahyphal bunches similar to those of Actinoplaca and resembling isidia (apothecia unknown), G. wesselsii Lücking, Sipman & Chaves, with verrucose thallus, dark greyish brown, applanate apothecia with single-spored asci producing muriform ascospores, and minutely spathulate, dark brown hyphophores with moniliform diahyphae, and Jamesiella chaverriae Chaves, Umaña & Lücking, with isidioid hyphophores (‘thlasidia’) which are flask-shaped and apically thinly ciliate (apothecia unknown). A further species, Gyalideopsis sp., with distinctly stipitate, umbelliform hyphophores, is not formally described due to the lack of apothecia and hyphophores. A further nine species are reported as new to Costa Rica: G. buckei, G. capitata, G. confluens, G. giganteoides, G. megalospora, G. napoensis, G. nepalensis, G. palmata, and Lithogyalideopsis zeylandica. A world-wide key to all presently known 94 taxa of Gyalideopsis and its recent segregates is presented, as well as a checklist.