In the past, the Bluish-slate Antshrike was sometimes treated as conspecific with the much wider and easterly distributed Cinereous Antshrike (Thamnomanes caesius), and indeed it was originally described as such. The two are generally regarded as forming a superspecies. The male Bluish-slate Antshrike is predominantly dark gray except the usually concealed white interscapular patch, and therefore much like the slightly paler-throated male Cinereous Antshrike, whereas females are quite different in their plumage. Whilst the female Cinereous Antshrike is largely warm brown throughout, females of the present species are largely gray above and over the head and throat, while the underparts are bright cinnamon-rufous. The Bluish-slate Antshrike inhabits the lower stories of lowland evergreen forest, both terra firme and seasonally flooded areas, mostly below 800 m, and like other Thamnomanes the species is a regular constituent of mixed-species foraging flocks. Both Dusky-throated Antshrike (Thamnomanes ardesiacus) and Saturnine Antshrike (Thamnomanes saturninus) can be found in the same flocks, depending on their location, but the Bluish-slate Antshrike usually forages at higher levels than either of the last two named species.