Adults are olive-gray on the upperparts with white underparts, with thin bills and short tails. They have white wing bars, a black stripe through the eyes and a yellow crown surrounded by black. The adult male has an orange patch in the middle of the yellow crown.
Their breeding habitat is coniferous forests across Canada, the northeastern and western United States, Mexico and Central America. They nest in a well-concealed hanging cup suspended from a conifer branch.
These birds migrate to the United States. Some birds are permanent residents in coastal regions and in the southern parts of their range. Northern birds remain further north in winter than the Ruby-crowned Kinglet.
They forage actively in trees or shrubs, mainly eating insects, insect eggs and spiders.
They give a series of high-pitched calls on a single note, and tend not to fear human approach.