The male Kentucky Warbler is a relatively chunky, short-tailed, and long-legged warbler. The upper parts are bright olive; the underparts entirely yellow. The distinctive face pattern is highlighted by a black crown, yellow eyebrow that curls behind the eye, large black patch on face. Bold yellow spectacles separate the black crown from the black on its face and sides of neck; the legs are pink. The female is similar to the adult male, but the black areas are duller, sometimes reduced. The juvenile birds are olive-brown above. The wings are olive with two brown wing bars. The head and neck are unmarked olive-brown. The underparts are yellow-brown, increasingly yellow on flanks and belly.

The song is a series of rolling musical notes, churry churry churry, with each note repeated about six times; resembling the song of the Carolina Wren, but lower in pitch and more slurred.
Calls: Primary call is a distinctive low, sharp chuck.

For nesting, the female chooses a site within minutes or up to one day after the pair becomes wedded. Most nests are usually hidden by overhanging vegetation or fallen branches, and built so that the base rests on the ground, sometimes partly anchored by a small shrub. When wedged in dead twigs near the ground, the base is within one inch of the ground.