It includes the marmosets and tamarins. Marmosets and tamarins are among the smallest primates, with head and body lengths as small as 130 mm and tails of 150 mm. The face is very sparsely furred or naked. The pelage is soft and silky, and often includes characteristic tufts of hair on the head.
Coloration is variable and in some cases quite striking to the human eye.
Unlike many other New World primates, marmosets do not have a prehensile tail. In form, callitrichids resemble other primates that cling vertically to trees. The forelimbs are shorter than the hind limbs, but most locomotion is quadrupedal. The hands and feet resemble those of squirrels. The thumb and big toe are not opposable.