This paper reports species of Serolis (Isopoda, Flabellifera) occurring on the continental shelf of southern Brazil. Five species are recorded. S. polaris Richardson, 1911 and S. laevis Richardson, 1911, new records from Brazil, are redescribed. S. uaperta sp. n., S. veaperta sp. n. and S. completa sp. n., are new to science. A full description of the female S. laevis is given for the first time. Furthermore, the nonidentity of this species with S. oonvexa Cunningham, 1871, is positively established. Family, generic and specific diagnosis are provided. Ecological and dis tributional notes, as well as a classification key based on adult specimens, are given for each species studied.