This species is a mid-sized true frog. Adult green frogs range from 5–10 cm (2.0–3.9 in) in body length (snout to vent, excluding the hindlegs). The typical body weight of this species is from 28 to 85 g (0.99 to 3.0 oz). Males have a tympanum twice the diameter of the eye and a bright yellow throat. Female tympanum diameter is about the same as that of the eye. Dorsolateral ridges, prominent, seam-like skin folds that run down the sides of the back, distinguish the green frog from the bullfrog, which entirely lacks them.
Green frogs live wherever there is shallow fresh water—ponds, road-side ditches, lakes, swamps, streams, and brooks. Most often seen resting along the shore, they leap into the water when approached. By inhabiting an ecotone, in this case the terrestrial and aquatic habitat boundary, green frogs (and other aquatic ranid frogs), by employing a simple leap, leave behind their many and faster terrestrial enemies that cannot similarly cross that boundary.
Green frogs breed in semi-permanent or permanent freshwater. Males call from and defend territories. The distinctive call sounds like a plucked banjo string, usually given as a single note, but sometimes repeated. The breeding season is from April to August. Actual mating involves amplexus, whereby the male grasps the female with his forelimbs posterior to her forelimbs. The female releases her eggs and the male simultaneously releases sperm which swim to the egg mass. Fertilization takes place in the water. A single egg clutch may consist of 1000 to 7000 eggs, which may be attached to submerged vegetation. Green frog tadpoles are olive green and iridescent creamy-white below. Metamorphosis can occur within the same breeding season or tadpoles may overwinter to metamorphose the next summer. Males become sexually mature at 1 year, females may mature in either 2 or 3 years.