The diversity of eriophyoid mites on ferns and conifers is notably lower than on angiosperms. To date, 40 eriophyoid mite species from 20 genera have been recorded on ferns. Most species belong to the eriophyid subfamilies Phyllocoptinae (45%), Eriophyinae (34%), and Nothopodinae (18%), while only one represents the diptilomiopid subfamily Rhyncaphytoptinae. The greatest diversity occurs on the fern orders Polypodiales and Cyatheales, followed by Equisetales, Gleicheniales, and Schizaeales, whereas no eriophyoid taxa have been described from Marattiales. We describe two new Eriophyidae species from ferns: Cymoptus ptisanis n. sp., collected in South Africa from erinea on the lower surface of frond pinnae of Ptisana salicifolia (Schrad.) Senterre et Rouhan (Marattiales: Marattiaceae), and Nothopoda vietnamensis n. sp., collected in Vietnam from galls on fronds of Nephrolepis cordifolia (L.) C.Presl (Polypodiales: Nephrolepidaceae). Morphological descriptions of the new taxa are supplemented with partial Cox1 (PV698368, PV698369) and 28S (PV711118, PV711119) gene sequences, photographs of host plant symptoms, and a series of images documenting stages of gall formation on Nephrolepis. In this paper we also propose relaxing the generic concept of Cymoptus Keifer 1946 (as Aceria-like eriophyines missing tibial seta l′ I), question the synonymy of the poorly differentiated nothopodine genera Floracarus Keifer 1953 and Nothopoda Keifer 1951, and advocate for future comparative studies on gallogenesis induced by eriophyoids on ferns and angiosperms.