Geoffrey’s spider monkeys are large-bodied primates with long, slender limbs and a long tail that is at least the length of their body, which is used as a fifth limb for grasping and swinging through the vines in the trees. Its fur is mostly black or dark brown, with lighter or reddish patches sometimes present on the chest and limbs, and distinctive black hands and feet, giving it its common name, the black-handed spider monkey.

Spider monkeys live in large groups with an advanced social system. They will break into smaller foraging parties that reunite later, allowing them to be flexible to the availability of food. They eat mostly fruit and are crucial to the ecosystem as they disperse seeds through their droppings. 

Spider monkeys have complex vocal communication, using their loud, long-distance calls to spread across the forest canopy and maintain the group.

Reproduction involves a gestation period of approximately 230 days (about 7.5 months), with females usually giving birth to a single infant. Mothers provide intensive care, carrying and nursing their young for up to a year or more; offspring remain dependent for several years before reaching sexual maturity around 5 to 7 years of age.