We describe a new species of the formerly monotypic genus Mesobaena from the northern part of the State of Pará, Brazilian Guiana. This species is characterized by having a very pointed snout, two supralabials and two infralabials, of which second ones are elongate and enormous, small eye visible under ocular, ocular very elongate, autotomy annulus poorly marked or absent, absence of dorsal, lateral and ventral sulci, and presence of vertical flat, unsegmented band-like structure with concave lateral edges on tip of tail. Hemipenis without spines or distinct ridges on proximal third, sulcus spermaticus only on proximal third. We make comparisons with other South American amphisbaenids, and provide a key to the amphisbaenids of the Guianan Region. The species is fossorial and inhabits Amazonian tropical rainforest forest near creeks. This is the second species known of the genus, which seems to be restricted to the Guiana Shield and immediate surroundings.