We describe three new species of Rectiostoma Becker, 1982 from northwestern Costa Rica: R. annemayae Heikkilä and Metz, n. sp., R. eowilsoni Heikkilä and Metz, n. sp., and R. philipmayi Heikkilä and Metz, n. sp. We used a data set of DNA barcodes (cytochrome oxidase I) accumulated for Lepidoptera collected at Area de Conservación Guanacaste (ACG) to initially delimit the species, then we confirmed identities with morphology of the male and female genitalia. We provide a neighbor-joining tree with supporting statistics, illustrations of adult specimens and their genitalia, and the first host plant records for Neotropical Rectiostoma species. We also include photographs of the larvae of R. annemayae and R. eowilsoni.