Male and female titi monkeys look the same. Both are chestnut brown with a gray, non-prehensile tail and black face.

The average weight for titi monkeys is about 2.2 pounds (1 kilograms). These monkeys typically have a total head and body length of around 13 inches (33 centimeter), with tails that are an additional one-third to one-fourth of this length.

Titi monkeys are found in Brazil in the Amazon River basin, in forests and swamps along river and lake shores in the lower tree canopy. They are arboreal and rarely come to the forest floor. Titis move through the understory of the forest quadrupedally, as well as by leaping. However, when feeding they sit vertically on branches and trunks. Titi monkeys generally stay in low canopy forest, near rivers. They may rest quietly in dense vegetation for long periods.

Titi monkeys can live into their early 20s.

Titi monkeys are considerably more vocal than most other Neotropical primates. Their vocalizations are also more complex than those made by most other monkeys. Pairs of titis have been known to engage in duets with other pairs at dawn.

This loud territorial call is composed of a series of short sequences of noises that sound like "chirrup-pump" and can be heard for up to 1.6 miles (1 kilometer). However, except during these territorial calls, they can be rather quiet.

These monkeys are a primarily fruit-eating species, but they also eat leaves, seeds and some insects. They forage in small groups that begin feeding in the early morning and continue throughout the day. A mid-day rest period typically interrupts their daily feeding.

At the Smithsonian's National Zoo, titi monkeys eat fruit, vegetables and greens and have access to crickets and mealworms.

Like most Neotropical primates, titi monkeys are strongly diurnal. They typically sleep together in a vine-encrusted tree and often return to the same tree night after night.

Family groups are strongly territorial. A family group consists of a monogamous adult pair and their offspring from several seasons. Juveniles leave their family group after two to three years.

Grooming is an important activity that serves to strengthen social bonds among members of the group. Family members groom each other often, especially during the mid-day rest.

Tail entwining—when two individuals sit with their tails wrapped around each other—is used to reinforce bonds amongst pairs. Tail twining is especially common between the adult male and female and takes place when two family members are sitting together. This is true whether the monkeys are awake or asleep.

Female titi monkeys give birth to a single offspring after a gestation of 160 days, with births typically occurring between November and March. Females give birth to about one baby a year. Young are weaned at about 8 months of age. The males helps care for the baby by carrying it when the female is not nursing.

Titi monkeys occur in a remote and isolated area absent of major threats. Currently, they can be found in several protected areas throughout their range.