Four species of Pinnotheridae inhabit European marine waters, Afropinnotheres monodi, Nepinnotheres pinnotheres, Pinnotheres pectunculi and Pinnotheres pisum. For these four species there are data available on the morphology of their larval stages as well as DNA markers. This information has allowed us to detect some larvae in plankton samples from the Gulf of Cadiz (SW Iberian Peninsula) that do not belong to any of these European pinnotherid species and to be confirmed by DNA barcoding. In this study these findings are shown as a case of early detection of a newly introduced and unknown species in European marine waters.