The carapace is a smooth, flattened oval, and is green to black in color, with red markings in some sub-species. The plastron is generally yellow, sometimes tinged with red, sometimes with a black to reddish-brown figure of varying size and shape. The skin of the painted turtle is black to olive with red and yellow stripes on the neck, legs and tail and yellow stripes on the head. Males have elongated foreclaws and long, thick tails.
Females have shorter foreclaws, shorter and thinner tails, and tend to be larger.
This turtle is unique in that the vertebral and costal scutes run virtually parallel, so the light bordered seams are aligned across the carapace. On all other North American turtles, the seams alternate. The plastron is usually plain yellow. In the coastal portions of its range, it may be found in brackish tidal waters. It has dark borders around its alternating carapacial seams, relatively ornate marginal scutes and a dark figure on its plastron.