The following species of the isopod genus Serolis are recorded from the continental shelf of southern Brazil: S. exigua Nordenstam, 1933, S. polaris Richardson, 1911, S. foresti Bastida & Torti, 1970 and S. inermis sp. n. S. exigua is for the first time recorded from off Brazil. Both S. polaris and S. foresti are recorded from new localities. S. inermis sp. n., a new species, is detailed described. Remarks are made on the importance and variations of some morphological features. The limit of distribution of both S. exigua and S. foresti is slightly extended northernwards.