Acrothamnion preissii is an invasive species in the Mediterranean Sea, and is listed among the 100 worst non-indigenous species. In July and August 2009, this non-native red macroalga was found for the first time in the Azores (on Santa Maria), and this represents the first record of this species in the Atlantic. Here, we describe the establishment of this invasive species in the Atlantic. In recent surveys, A. preissii displayed an invasive behaviour. As suggested for the Mediterranean Sea, hull fouling is the most likely vector for its introduction into the Azores.