Tahuantinsuyoa chipi sp. n. is distinguished from its only congener, T. macantzatza, by having a simple spot on the head at the posterodorsal margin of the orbit instead of an intensely pigmented caudal directed stripe from the orbit to the midline of the nape. Collections are from the Rio Pachitea drainage. Preliminary observations suggest that Tahuantinsuyoa species develop a bone canal through the anterior ceratohyal for the hyoid artery and this may indicate closer relationship to the Pacific versant species ‘Aequidens’ rivulatus than to Amazonian chichlasomines. Thirteen species and three genera of fishes are known only from the Pachitea (six species, no endemic genus) or Aguaytia (four species, two genera) or both drainages (three species, one genus). Insufficient collecting in nearby rivers prevents the conclusion that the two rivers would have markedly high endemism or be particularly closely related faunistically among the Ucayali tributaries.