Recently, using morphological and molecular analyses, several Pseudopolydora specimens (Polychaeta: Spionidae) from French coastal waters were identified as Pseudopolydora kempi ssp. japonica Imajima and Hartman, 1964. According to the samples examined, P. kempi ssp. japonica has been present in European waters since 2004. Previous misidentifications in France are likely due to its resemblance to the indigenous species Pseudopolydora pulchra (Carazzi, 1893), and to the status of P. kempi ssp. japonica which is still controversial. Material was collected from Arcachon Bay, Morbihan Bay, Aiguillon Bay, and in the Gironde estuary (Bay of Biscay, France). All these areas have extensive shellfish industries, especially the farming of the Japanese oyster Magallana gigas (Thunberg, 1793). The importation of these live oysters from Japan has often included other species including polychaete worms, indicating a major vector of exotic species.