A new species of Otocinclus, Otocinclus tapirape, is described. The new taxon differs from other species of the genus by the following combination of characters: low number of trunk lateral plates; canal-bearing plates of trunk median plate series truncated, restricted to the anterior field; presence of iris diverticulum; expanded subnasal lamina on lateral ethmoid; and nuchal plate narrow. The phylogenetic relationships of the new species are ((Otocinclus affinis, Otocinclus flexilis)(Otocinclus xakriaba (Otocinclus tapirape, remaining Otocinclus species))).