Storeria dekayi, commonly known as the DeKay's Brownsnake, is native to North America. Its distribution extends across parts of Canada, the United States, and Mexico. In Canada, it is found in parts of southern Ontario and southwestern Quebec. In the United States, the DeKay's Brownsnake is widespread, found from New England to Minnesota and south to Florida and Texas. In Mexico, its range extends into the northeastern regions.

The DeKay's Brownsnake typically inhabits environments that are moist and well-vegetated. It favors habitats such as woodlands, marshes, fields, and suburban areas with abundant ground cover. The presence of leaf litter, logs, and rocks is essential for providing shelter and hunting grounds. The climate in these habitats varies but generally includes temperate environments with adequate moisture.

Storeria dekayi occupies a niche as a small, primarily terrestrial snake. It plays a role in controlling the populations of its prey, which includes earthworms, slugs, and other invertebrates. Its ecological niche is closely tied to environments that offer both protection from predators and a rich supply of small invertebrates. As a predator of small soil-dwelling animals, this species contributes to soil aeration and the promotion of plant growth through its feeding habits.