Small flycatcher with bright white tail panels. Male is blue overall with an off-white belly. Female is brown with a pale belly and a neat white throat “bib.” Both sexes have white undertails and two white streaks on the uppertail, most evident when flashed in flight. Male is similar to Hainan Blue Flycatcher, but White-tailed is more extensively blue overall, with a squatter appearance. Songs and calls both incorporate a loud, short whistle which recalls a rusty gear squeaking.