The fern genus Didymochlaena is characterized by having scaly rhizomes and petioles, tufted and bipinnate leaves, dimidiate pinnules, and fewer than 11 sori per pinnule. For a long time only one species was widely recognized in the genus. Most recently, six and seven species from Madagascar and Asia-Pacific regions, respectively, have been recognized based on morphological and/or molecular evidence. In this monographic study we recognize 22 species worldwide, six of which are described as new: D. alpina, D. amazonica, D. cameroonensis, D. comorensis, D. cubensis, and D. mesoamericana. A key to all species is provided, and detailed descriptions, illustrations, and information on their distribution and habitats are given.