Cardellina pusilla, commonly known as the Wilson's Warbler, is native to North America. It predominantly breeds in the boreal forests of Canada and other northern regions of the continent, extending down through parts of Alaska and the northwestern United States. During winter migration, the species moves southward, primarily to Central America and the northernmost parts of South America, including countries like Mexico and Guatemala.

Wilson's Warbler is often found in thick undergrowth of riparian woodlands, bogs, and shrubby habitats near water sources during the breeding season. These areas typically have cool, moist conditions. During the non-breeding season in winter, it occupies tropical and subtropical moist lowland and montane forests, often favoring areas with dense vegetation.

Wilson's Warbler plays a role in the ecosystem as an insectivore, feeding primarily on insects and other arthropods. This diet helps regulate insect populations in its habitat. The species is also a prey item for larger birds and small mammals, contributing to the food web dynamics of its environment.