Sphaeroma serratum (Fabricius, 1787) has its first occurrence recorded from Brazil, by means of especimens collected at rock shores of Marina da Glória, Baia de Guanabara, Rio de Janeiro. The species is redescribed with illustrations. Structural patterns of pigmentation of studied population are here presented.
Isopoda; Sphaeromatidae; Sphaeroma serratum; taxonomy; redescription; patterns of pigmentation; Brazil