We present the first record of two nonnative Bivalvia species originally from North America, Mercenaria mercenaria and Ensis directus, in the waters of the Iberian Peninsula (southwest of the Bay of Biscay). This constitutes the southernmost distribution for these species in the northeast Atlantic to date. We provide notes on the relative abundance, depth range, and substrate preferences of the species in their new habitat. The bivalve E. directus has became the dominant Ensis species along the Cantabric sandy shores it has colonized.