The other species lack a well-developed squamosal crest. The ears are relatively long in U. caudimaculatus and U. anak but short in the remaining three species. The teeth of Uromys are similar to those of Melomys but much longer. The incisors are large and powerful, with uppers and lowers being about the same size. The hands and feet are broad and well clawed.
Females have two pairs of mammae.
Giant naked-tailed rats are arboreal and are excellent climbers. Their tail is not truly prehensile but does facilitate climbing by curling over limbs and gripping with the rasplike scales. Nests are usually made in hollow trees, though U. caudimaculatus sometimes seems to raise its young on bare rock in caves or old mine tunnels. The diet consists of coconuts, other nuts, fruits, and flowers. Litters of U. caudimaculatus have been recorded in New Guinea during November and December and may contain one to three young.