Etjoia was discovered in the upper beds of the Omingonde Formation of Namibia (dated to the Ladinian to Carnian) by American paleontologist Charles Schaff in 1996.

The specimen was unearthed on the south-eastern side of the Etjo Mountain, in the Waterberg Basin of the Otjozondjupa region, in central north-west Namibia.

The floodplain was subject to short, wet winters with heavy thunderstorms followed by long, warm, and dry summers during which dust storms occurred frequently.

[2] Etjoia was coexisting with small herbivorous kannemeyeriid dicynodonts and the apex predator Cynognathus, a large carnivorous cynognathian.

Below is a cladogram from Hendrickx et al. (2020)[1] showing the phylogenetic relationships of Diademodontidae, Trirachodontidae (here recovered as paraphyletic), and early diverging Traversodontidae:Thrinaxodon Cynognathus Diademodon Titanogomphodon Langbergia Trirachodon Beishanodon Sinognathus Cricodon