Three new species of the genusPlatofrom caves in the states of Pará and Minas Gerais, Brazil, are described.P.novalimasp. n., from Minas Gerais, is the first record of the genus in the southeastern region of Brazil.P.ferriferussp. n.andP.striatussp. n., from Carajás, Pará, north of Brazil, are also described. The former is an extremely abundant species, whereas the latter has only one known male specimen.Cuacubagen. n.is proposed and represented by two new species,C.marianasp. n.(type species) andC.morrodopilarsp. n., both from the state of Minas Gerais. Morphology of genitalia inCuacubagen. n.is similar to other Theridiosomatidae genera and is herein discussed. None of the proposed species presents troglomorphic adaptations. They are widespread, abundant inside caves in different and large karst areas, and each genus prefers different lithologies.