The Brazilian rainbow boa is a round-bodied terrestrial boa of medium build. The head is not particularly large, but it is distinctly wider than the neck. It is soft-skinned with great iridescence in its skin. Brazilian rainbow boas are brown or reddish brown. There are 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 individuals of this species.  Adult males have substantially larger spurs along the side of the vent and also have noticeably thicker bases of their tails due to the invaginated hemipenes. These boas range from 3.25 to 6.5 feet (1 to 2 m) in length.