Abstract Diapterus brevirostris (Sauvage, 1879) is a fish of the family Gerreidae, native to the tropical and subtropical waters of the Pacific coast of America. A specimen of this species was captured off the coast of Asturias, Spain. To the best of our knowledge, this is the first record of the genus Diapterus in the North Atlantic. Given its small size (6.4 cm), it is likely that the species was present in the area for a relatively short time. Although the introduction pathway is unknown, the species' native area and the proximity of a major port to the site of capture suggest that ship's ballast water is the most likely vector of introduction.