Adults have greenish upperparts and yellowish underparts (especially on the throat), with a dusky wash on the chest.

They have a white or yellow eye ring that lacks the teardrop projection of Pacific-slope (E. difficilis) or cordilleran (E. occidentalis) flycatchers, white or yellowish wing bars that contrast strongly against the black wings, a broad, flat bill, and a relatively short tail when compared to other members of the genus.

DNA testing in 2014 confirmed a field mark, involving the extent of buffy edging on the secondaries, to reliably distinguish this species from the two so-called "Western Flycatchers.

"[2][3] Measurements:[4] Yellow-bellied flycatchers wait on a perch low or in the middle of a tree and fly out to catch insects in flight, sometimes hovering over foliage.

Their breeding habitat is wet northern woods, especially spruce bogs, across Canada and the northeastern United States.