A new species of Leposoma is described from Ilha do Lago do Prato and Ilha do Açaí, Arquipélago das Anavilhanas, in the lower Rio Negro, state of Amazonas, Brazil. Like all members of the parietale group, it differs from all species of the scincoides group by having wider and shorter dorsal scales and ventrals arranged in regular longitudinal rows. It is further characterized by having conic granules on the sides of neck, three enlarged pairs of chin shields, absence of granules between superciliaries and supraoculars, a longer than wide interparietal with lateral margins almost parallel, 42–44 transverse dorsal rows (the highest number in Leposoma), gular scales small in 13–15 rows (less than 11 in other Leposoma), 30–33 scales around body, 26–27 ventrals, two preanal and four femoral pores on each side in males, one preanal and no femoral pores in females, 13–14 and 19–21 lamellae under finger IV and toe IV, respectively. The new species is sympatric with Leposoma guianense and Leposoma percarinatum and is more similar to the latter.