This is the first record of the spiny-cheek crayfish, Orconectes limosus (Rafinesque, 1817), introduced into the Iberian Peninsula. Sixteen individuals of this crayfish species were detected in the Muga River, near to the Boadella Reservoir (Catalonia, NE Iberian Peninsula) on October 9, 2010. This reservoir is only 14 km away from France, where the spiny-cheek crayfish was introduced during the 20th century. The presence of this non-native crayfish is a pressure on the conservation of native crayfish populations of this area and a problem for the whole aquatic ecosystem.