This soft-skinned boa has beautiful, iridescent skin. Tiny ridges on the scales act as prisms to refract light and create a rainbow-colored effect. Brazilian rainbow boas are brown or reddish brown snakes with three parallel black stripes on the top of the head and large black rings down the back that give the appearance of dorsal blotches.
The round lateral blotches are black with an orange or reddish crescent across the top.
There is a great deal of variation in color and marking among this species. Adult males have substantially larger spurs along the side of the vent and have noticeably thicker bases of their tails due to the internal hemipenes, their sexual organs. invaginated hemipenes.