It is found throughout sub-Saharan Africa, excluding the drier areas of South Africa, Botswana, and Namibia, where it inhabits subtropical or tropical dry forest, subtropical or tropical moist lowland forest, and savanna.

It has a disputed generic placement, with different authorities variously putting it in Muscicapa, Fraseria, or other genera.

They forage in the upper levels of the canopy, catching prey in flight and from foliage, bark, and leaves.

The ashy flycatcher was originally described as Butalis caerulescens by the German ornithologist Gustav Hartlaub in 1865, based on specimens from South Africa.

The specific name of the species refers to its colour, meaning dark blue or cerulean in Latin.

[4] Ashy flycatcher is the official common name designated by the International Ornithologists' Union (IOU).

[5][7] The authors of the 2016 study suggested placing these two species in either Cichlomyia or Butalis, depending on which one has priority.

[6] A more recent molecular phylogenetic study published in 2023 supports the placement of the species in Fraseria.

The grey tit-flycatcher can be distinguished from the present species by a combination of its white-edged dark tail and foraging behaviour; the grey tit-flycatcher gleans insects from leaves, compared to the ashy flycatcher's more active method of sallying for insects.

The African dusky flycatcher can be told apart by its larger head and more rounded, dumpy, and, according to some observers, "cuter" appearance.

The white-eyed slaty flycatcher also has a more prominent white eye-ring, although the extent of the ring varies between individuals and may not be diagnostic.

[7] The ashy flycatcher's calls include short peeps and chirps, a high-pitched wheeze, and other notes.

A distress call, consisting of a shrill, high-pitched, and buzzing note, is given when birds are in panic or stressed.

[7] Its diet consists of mostly insects, mainly beetles, flies, grasshoppers, adult and larval moths and butterflies, winged ants, and termites.

Nests are generally built at heights of 2–15 m (7–49 ft) in crevices, cavities, or forks in trees, or sometimes in holes or ledges in walls.

They are built by both sexes and consist of a sturdy "cup" made of moss, grass, rootlets, shredded bark, fibers, and spiderwebs.