Corsiaceae is recorded for the first time in the Peruvian flora, based on recent collections of Arachnitis uniflora from the cloud forests of the southern Peruvian Andes. Our record extends considerably the distribution of this taxon in around a 500 km straight line to the northwest. The species is now known from Patagonia to southern Peru, in very diverse habitats. The discovery of this family in the Machu Picchu Sanctuary boosts the already well-known importance of this protected area regarding its highly rich plant diversity.