Goeldi's monkeys are covered in shaggy, black hair, with lighter coloration around the face. They have claw-like nails on all of their digits, except for their large toes. These monkeys are the only species in their genus, Callimico. And although they are members of the callitrichidae family, which includes tamarins and marmosets, they have several characteristics that set them apart.

Goeldi's have three molars instead of two. They give birth to singletons rather than twins, and males take on less of a child-rearing role than marmoset or tamarin fathers. Goeldi's also have a larger range than other callitrichids and are the only primates known to eat mushrooms as a substantial (albeit seasonal) part of their diet.

These vertical climbers and leapers can reportedly leap a distance of about 13 feet (4 meters) horizontally without losing height. They can leap from one tree to another, turn in flight and grab their target, Goeldi's monkeys travel roughly 1.2 miles (2 kilometers) per day in a circular pattern and within a territory of about 740 to 1,975 acres (30 to 80 hectares).

Their diet consists primarily of fruits, insects and small vertebrates. Groups will travel and feed in fruiting trees, but these monkeys also hunt individually, leaping to the ground to find small vertebrates. Unlike any other New World monkey, Goeldi's are known to rely heavily on mushrooms during the dry season when fruit is scarce.

At the Smithsonian's National Zoo, Goeldi's monkeys eat fruit and vegetables, high-fiber monkey chow, canned marmoset diet, crickets and mealworms.

The International Union for Conservation of Nature lists Goeldi's monkeys as vulnerable, as of a 2008 analysis. Potential for habitat loss is considered their primary threat; the most recent assessment found that their region was stable but expected to rapidly decline due to proposed plans fro human development and logging. This anticipated loss of habitat, combined with the species' already fragmented populations, has resulted in their vulnerable classification. Goeldi's monkeys are also affected by hunting and trapping.

These monkeys can be found in multiple protected areas around Brazil, Colombia and Peru. They are also listed on CITES Appendix I, which helps to limit their trade.