It has a rounded head and a thick, soft coat and frequently adopts a characteristic posture with the body hunched, limbs close together, and a tail hanging down.

It is diurnal and moves in pairs or family groups, which communicate by means of a wide repertoire of sounds.

Its upper incisors are elongated and the incisiform canines barely extend beyond the other teeth.

The upper molars are sometimes tricuspid and the lower premolars are relatively simple.

The skull is orthognathous, orbits are unfenestrated, balls are inflated ventrally, and a large sinus found above the nasal.

The foramen magnum is located towards the front, and the atlas has shallow anterior articular facets which allow the condyles to attach.

The premaxilla is short, giving the appearance of a small, not especially prognathic face relative to other platyrrhines.

It has been suggested that grooming is a form of habituation introducing the concept of presence and physical contact with companions.

Adults and juvenile also intertwine tails with the opposite sex whenever two from the same social group are by each other.

The red-bellied titi has a variety of postures and facial expressions that it uses as visual signals.

Other signals associated with hostility include piloerection and tail lashing.

The adult males are responsible for carrying the infants except when the young is being nursed or licked.