This communication describes the first records of byssal hairs on the postlarvae shells of Mytilusedulisplatensis d'Orbigny, 1842. The postlarvae used in this study were sampled on artificial collectors used for mussel culture in San Jorge Gulf, Sudoccidental Atlantic Ocean. A general description of the hairs is made as well as an exploratory analysis of their spatial distribution on the shell surface. The presence of these byssal hairs is suggested as a criterion to differentiate M.edulisplatensis from other mytilids.