In this study, a new species of Hyalella is described from southern region of Brazil. Hyalella jaboticabensis n. sp. was recorded in the municipality of Jaboticaba, northwest region of state of the Rio Grande do Sul, southern Brazil. This species is characterized by showing smooth body surface, epimeral plates not acuminated, inner face of the gnathopod 1 with nine or ten serrate setae and some simple setae (six to eight), inner ramus of uropod 1 of males with one short curved seta, peduncle of the uropod 3 with six cuspidate setae with an accessory seta and two or three cuspidate setae on the rami, telson as long as wide (square) with six to eight short and long cuspidate setae with an accessory seta. This new description increases the Brazilian known diversity of species of Hyalella to 42 (25 to southern Brazilian region) and 108 species in the Americas. It is noting that it is crucial to know the complete diversity of Hyalella genus, and to consider conservation measures to protect species like H. jaboticabensis n. sp., endemic to two single small streams.