The head and body length of Linnaeus's Two-toed Sloth is 540-740 mm, and the tail is absent or vestigal. Weights range from 4.0-8.5 kg. Coloration is grayish brown with a pale face, and during the wet season, algae growth can produce a greenish cast in the coat. This growth may provide nutritional benefits through skin absorption or licking the fur, in addition to helping camouflage the sloth. Each limb terminates in a long curved foot. The forefeet have only two digits which are bound by skin the entire length. The hind feet have three, which are hooklike claws. They are used to suspend the animal from tree branches and unlike Three-toed Tree Sloths, these mammals spend almost their entire lives upside-down. They eat, sleep, mate and even give birth in this position. When sleeping, they rest their head between the foreleg, on the chest. The feet are so close together, the animal looks like a bunch of dried leaves. They are almost entirely arboreal and nocturnal, coming down to the the ground about once a week to urinate and defecate. They are good swimmers, employing a sort of breast stroke.

Linnaeus's Two-toed Sloths have the lowest and most variable body temperature of any mammal, ranging from 24°C to a high if 33°C. Thus they inhabit equatorial tropical forests of constant temperatures eating fruits, leaves, and tender twigs, using their arms to pull the food toward them. They are most vulnerable when on the ground, falling prey to jaguars, ocelots, and other cats. In defense they use their sharp claws and teeth, and can inflict severe wounds.

Sexual maturity in females occurs at 3.5 years and in males at 4-5 years. Gestation is about 5 months and the infant weighs 350-454 grams at birth. At 5 months the young feeds independent of its mother, but may continue a close association with each other until 2 years of age.

The distribution of Linnaeus's Two-toed Sloth is in the Guinas and Venezuela (delta and south of Rio Orinoco) south into Brazil (Maranhao west along Rio Amazonas/Solimoes) and west into upper Amazon Basin of Ecuador and Peru.