We examined nest tree preferences of northern flying squirrels (Glaucomys sabrinus) in an old-growth, mixed-conifer forest of Yosemite National Park, California. We tracked 8 individuals to 21 nest trees during July through September 2004. Flying squirrels selected nest trees that were larger in diameter and taller than either large nearest-neighbor or random trees. Flying squirrels showed no tree species preference, but used snags more often than live trees relative to their availability. Nest trees were not closer to perennial creeks than random trees. Results suggest that northern flying squirrels of Yosemite National Park might require large trees and snags, but unlike more xeric parts of the extreme southern Sierra Nevada, they might not be constrained by proximity to perennial streams.