With a length of 32 to 45 cm and an average weight of about 0,8 kg (females) to 1,2 kg (males), they are the smallest Old World monkeys. Its fur is greenish gray above and whitish below. The head is round, with relatively large and prominent ears, a short nose and a hairless face.

It has a multimale-multifemale social system. The groups are of 20 to 70 individuals that are subdivided into smaller ones, possibly family nuclei, with little hierarchy. These subgroups are made up of males, females with young, and juvenile females. They are not territorial.

They are diurnal and arboreal. They sleep in trees near rivers and swamps. When they are stalked by a predator they jump into the water and swim. During the night the subgroups subdivide and form groups of 3-4 individuals, and when they wake up they form the subgroup again. During the day, when the group rests, adult females and young are located in the center of the group while males and juveniles are located on the periphery.

Their vocal repertoire is limited, their contact voices are dove-like and they are emitted when moving or searching for food.

The mating season goes from January to March and the birth season from June to August. During heat, the female's perineum acquires its maximum swelling for a period of 2 to 6 days and during pregnancy it turns red. After approximately 160 days of gestation, they give birth to a single calf. The newborn is large and well developed (200 g, which represents ¼ of the mother's weight) and develops rapidly. In less than 6 weeks he is able to eat solid food, and is independent at 3 months.