We describe two new species of the genus Hyalella found at Parque Estadual Tur & iacute;stico do Alto Ribeira (PETAR), a state park in Southeastern Brazil, and also redescribe H. caeca, the first cave species of the genus described in Brazil. Hyalella caeca is endemic to Tobias de Baixo Cave and is threatened according to the International Union for Conservation of Nature (IUCN) Red List; its original description lacks important and detailed morphological features. Hyalella caeca is completely blind and depigmented, with antenna 2 almost half the body length, maxilla 1 with nine serrate setae on the outer plate, gnathopod 1 with polygonal pattern on the dactylus, gnathopod 2 with a slender posterior excavation and uropod 3 subequal in length to the peduncle of uropod 2 and the telson. The two newly described species are found at Santana Cave and in epigean stretches of Rio Roncador River, and their morphologies differ greatly. Hyalella ceciliae sp. n., a troglobitic species of Santana Cave, is blind and depigmented, with elongated antennas and legs; its main features include antenna 2 more than half the body length, maxilla 1 with eight serrate setae on the outer plate, gnathopod 1 of male and female identical, with comb scales on the merus, and uropod 3 longer than the telson. Hyalella roncador sp. n., an epigean species of Rio Roncador River, has pigmented eyes, and its main features include antenna 1 half the size of antenna 2, maxilla 1 outer plate with nine serrate setae, gnathopod 1 propodus with polygonal pattern, gnathopod 2 palm with slender posterior excavation, and uropod 3 subrectangular, ramus with an excavation with cuspidate setae midway to the apex. Both species are protected by law, since the type localities are inside PETAR; however, Hyalella ceciliae sp. n. shows low abundance and is rare in the Santana Cave.http://www.zoobank.org/urn:lsid:zoobank.org:pub:4B42C2CB-FF06-4FD0-BF49-EDDF1983EAD1
