The occurrence of the brown mussel Perna perna is reported for the first time from the European Atlantic coast, on the southern Portuguese coast. Several specimens of this mytilidae species were identified in exposed rocky intertidal habitats in Vilamoura (37°04′19.70″N 8°07′19.71″W) and Ilha do Farol (36°58′29.38″N 7°51′42.51″W). It is suggested that, under warming climate conditions, this subtropical/tropical species might have extended its geographical distribution from North Africa.