Nests are used by many species for rearing offspring, thermoregulation and predator avoidance, and are thus critical resources, especially in cold climates. I examined the nest tree and nest site use by a population of northern flying squirrels (Glaucomys sabrinus), a secondary cavity nester and species of management interest, along the Rocky Mountain foothills in Sheep River Provincial Park, Alberta, Canada. Northern flying squirrels in this study area nested most often in tree cavities (∼63%) located in large snags and aspens (Populus tremuloides). Northern flying squirrels selected nest sites surrounded by less canopy cover and more large snags than random sites. As such, northern flying squirrel populations in cold climates may be constrained by specific habitat characteristics.