Males are azure blue on the back and white on the belly. An identifying mark is a dark blue or black line across the throat. They have dark streaking on the flanks and back. Females are dull gray-blue above with a yellowish wash below. Both sexes have two white wingbars.
Juveniles are brownish-gray above, with a pale center crown stripe and entirely white underparts. Cerulean warblers molt into an adult plumage prior to the breeding season following their hatching year.
Because the cerulean warbler often remains concealed in foliage high in the forest canopy, it is usually best identified its voice, a rapid series of buzzy notes on one pitch, with a rising "zeeeeee" at the end. The call is a sweet "chip."