Isertia psammophila, a new species from the white-sand campinarana forests in Northern Brazilian Amazonia is here described and illustrated. While molecular evidence indicates that it is closely related to I. rosea, I. parviflora and I. spiciformis, morphologically it is most similar to I. rosea by its short stipules and glabrescent leaves. Isertia psammophila occurs in sympatry with I. rosea and I. parviflora in the Viruá National Park, Roraima, Brazil, and these three species can be easily differentiated by morphological characters, which are here discussed.