A new species was detected during the examination of specimens of Doliocarpus for the Flora of Ecuador, which is is described and its morphological relationships with its closest allied species are discussed. Doliocarpus renneri, from the wet riverine forests of the Cuyabeno (Napo) river, is most similar to D. multiflorus, but differs from that species in its branches, branchlets and petioles covered by black trichomes, the obovate or elliptic-obovate leaves, the shorter inflorescence, the sessile flowers, and the sepals and petals that differ in shape and number. A previously described subspecies is elevated to the rank of species (i.e., Doliocarpus dasyanthus subsp. robustus to D. robustus), and an updated key to the species of Doliocarpus of Ecuador is provided.