The black redstart is 13–14.5 cm in length and between 12 to 20 grams in weight. The adult male is overall dark grey to black on the upperparts and with a black breast; the lower rump and tail are orange-red, with the two central tail feathers dark red-brown. The belly and undertail are either blackish-grey or orange-red. The wings are blackish-grey with pale fringes on the secondaries forming a whitish panel. The female is grey overall except for the orange-red lower rump and tail.

The species is socially monogamous. A male pairs with a female to rear young, guards her against other males, and mates with other females.

The black redstart prefers to inhabit stony ground mountains, or similar urban habitats, and large industrial complexes that offer cliff-like structures.