The Crescent-chested warbler is similar to both the Northern Parula and the Tropical Parula, with yellow underparts, a gray head, and greenish back. Its definitive characteristic is a chestnut crescent on its breast, less prominent in the aforementioned species. Juvenile males look similar to the duller adult females, while juvenile females may lack the chestnut crescent.
These monogamous, solitary birds become more gregarious in winter, joining mixed-species flocks to feed (mostly insects, but sometimes fruits and berries in the middle to upper levels of trees). It jumps from twigs and foliage, picking food from the underside of leaves, and hanging beneath leaves in a fashion similar to chickadees to check surfaces for prey.
Crescent-chested Warblers make their nests atop grassy tussocks or sheltered by a hill or bank near the ground. Usually they will have 1 - 2 broods a year. The female is believed to build the nest without help from the male, gathering moss, grass, conifer needles, and fine materials to line the nest. She will then lay approximately three plain white eggs. Incubation is estimated to last 12 - 14 days by the female. The chicks are altricial and are also brooded by the female, and fed by both sexes. The young stay in the nest for an estimated 8-10 days.