Rhagomys longilingua is one of the rarest sigmo-dontine rodents of South America, currently known from only 2 localities (4 individuals) in Peru and Bolivia. Here we report 3 additional localities in Peru, one of which extends the geographic distribution range of this species 613 km northeast from the type locality (Suecia, Manu National Park, Cusco department). Potential distribution models showed the presence of R. longilingua from Bolivia until Colombia along the eastern slope of the Andes.