The Least Flycatcher breeds in Canada and the northern United States from the Rockies eastwards and migrates during the winter to Central America from Mexico to Panama. It is found in forest, secondary forest and clearings. See the distribution map at Birdlife International.

It feeds on insects and occasionally fruit. The small delicate bill compared to many other flycatchers shows that its insect prey is usually small flies and gnats rather than larger insects.

This bird is duller than most illustrations because its plumage is worn. On migrating north to breed the plumage will freshen and the wing-bars will become wider.