The Atlantic titi is part of the genus Callicebus which is composed of thirteen species and sixteen subspecies.

Some more recent classifications of titis recognise many more species, and split the genus into three separate genera.

The states they have been documented to dwell within include Bahia, Espírito Santo, Minas Gerais, Rio de Janeiro, and São Paulo.

[6] Of all the Callicebus species, Atlantic titi monkeys have the largest geographic range except for C. torquatus, covering approximately 1,000 kilometers.

[4] The three subspecies of Callicebus personatus are products of clinical differentiation (when certain portions of the population are cut off from the parental stock due to an ecological barrier such as a river and are thus completely genetically isolated from one another).

The characteristic pigment of the Callicebus is eumelanin (dark brown or black) found in the iris, skin, and hair (usually on the forehead, crown and tail).

Due to their frugivorous nature, they have rarely been observed on the ground foraging for insects or small vertebrates.

[7] Because they prefer not to be on the ground, researchers have observed them eating soil found atop ant mounds.

[8] The use of disturbed and undisturbed forest by masked titi monkeys Callicebus personatus melanochir is proportional to food availability.

It is difficult to distinguish between the sexes externally, however Atlantic titi family dynamics indicate that the father carries the infant at all times during the nursing.

The defend their territories by loud intergroup vocalizations to other groups of monkeys and to other animals in the general area.

Additionally, all titi monkeys have "Dawn Calls" in the mornings in which the male and female usually duet the same song.