They are easily distinguished from other sea turtles because they have a single pair of prefrontal scales (scales in front of its eyes), rather than two pairs as found on other sea turtles.
Head is small and blunt with a serrated jaw. Carapace is bony without ridges and has large, non-overlapping, scutes (scales) present with only 4 lateral scutes.
Body is nearly oval and is more depressed (flattened) compared to Pacific green turtles. All flippers have 1 visible claw. The carapace color varies from pale to very dark green and plain to very brilliant yellow, brown and green tones with radiating stripes.
The plastron varies from white, dirty white or yellowish in the Atlantic populations to dark grey-bluish-green in the Pacific populations. Hatchlings are dark-brown or nearly black with a white underneath and white flipper margins.
For comparison, the Pacific green turtle (aka Black Sea Turtle) has a body that is strongly elevated or vaulted and looks less round in a frontal view than other green sea turtles.
The color is where you see the biggest difference with Pacific greens having a dark grey to black carapace and the hatchlings are a dark-brown or black with narrow white border with white underneath.