The Atlantic Leatherback is easily distinguished from the other oceanic turtles by its smooth leather-skinned carapace, which has 7 prominent longitudinal keels. The carapace varies from brown to black, as do the head and neck. The flippers are black but may have some white blotches. The plastron is white with some black blotching. Adults usually range from 137 to 178 cm in length and weigh 295 to 544 kg.
Larger individuals are uncommon.
This species has its throat lined with backward-pointing spines, an adaptation that enables it to feed extensively on jellyfish. Leatherbacks can possibly be harmed by ingesting man-made debris that looks like jellyfish. Many people have stopped releasing helium ballons into the air because of this. The Atlantic Leatherback is by far the most common sea turtle recorded in Nova Scotian coastal waters. This may be due to the huge size and the fact that they frequently become tangled in fishing gear.