A new species of the Hypsiboas benitezi group is described from the western Amazon Basin. The new species is characterized by its medium size (SVL 24.4–31.2 mm in adult males, 26.0–36.0 mm in adult females), absence of nuptial excrescences, palpebral membrane lacking golden reticulation, and a mental gland in males. The dorsal surfaces of living frogs are bright yellowish green to tan, and frequently bear an X-shaped mark; the parietal peritoneum, pericardium and sclera are covered by guanophores. The new species differs from other members of the Hypsiboas benitezi group (H. benitezi, H. lemai, H. microderma, H. pulidoi, H. rhythmicus, and H. roraima), by the combination of a dorsal X-shaped marking, absence of golden reticulation on palpebral membrane, and central portion of abdominal parietal peritoneum, pericardium, and sclera covered by guanophores. The new species has been confused with Hyloscirtus albopunctulatus (as Hyla albopunctulata) in the past, but the study of the type series of the latter indicates that they represent different species. Hypsiboas hutchinsi is excluded from the H. benitezi group and transferred to the H. semilineatus group, as it shares with H. geographicus and H. semilineatus the absence of a projecting spine in the prepollex (the only known species of Hypsiboas with this character state), presence of pigmented nuptial excresences, reticulated palpebral membrane, and finely tuberculated skin.