Unpatterned and green above, white to pale yellow below, the smooth green snake is difficult to confuse with any other snake in Massachusetts. Young snakes are dark olive or blue-gray in color and could be confused with young black racers except that racers have a mottled pattern when young. The smooth green snake has scales that are not keeled.

Green snakes emerge in April or May and mate in the late spring or summer. Eggs are laid from June to September, perhaps in two clutches of 4-6 eggs. Females probably incubate the eggs inside their bodies before depositing them in rodent burrows, sawdust piles, mounds of rotting vegetation or rotting logs. As a result, the eggs hatch 4-23 days after they are laid, a short period of time relative to other snakes.

Areas that support a ground cover of thick green vegetation are the preferred habitats of green snakes. Fields, wet meadows, bogs, marsh edges and open woodlands provide the kind of concealment cover required by these small snakes. Active during the day, green snakes feed on a variety of arthropods (crickets, grasshoppers, caterpillars, beetles, spiders, centipedes and millipedes). Green snakes rarely bite when handled and when they do, rarely break the skin. If handled roughly enough they will, like other snakes, exude a foul substance from their anal glands.