The voice has a variety of high-pitched trilling and staccato calls. Marmosets are diurnal, sheltering at night in tree holes and cavities. Most of their time is spent in trees or shrubs, though Callithrix argentata in the Matto Grosso sometimes goes into tall grass. They are active and agile, running, jumping, and occasionally leaping among trees and shrubs. Leontopithecus is said to bound from tree to tree with remarkable rapidity.
Movements are usually quick and jerky.
When at rest, marmosets sometimes draw the fingers inward, so that the clawlike nails pierce the bark of the support, and rest with the belly in contact with the branch, all four limbs hanging on either side. They are fastidious in the care of their pelage and engage in both individual and mutual grooming, the former being more common. The hands are used in securing food but not invariably for conveying it to the mouth. Marmosets and tamarins live in small groups. Contrary to what is sometimes reported, they do not have a monogamous mating system.