Original description as Chromis williamsi:
- Günther, Albert C. L. G. 1893. "Second report on the reptiles, batrachians, and fishes transmitted by Mr. H. H. Johnston, C. B., from British Central Africa". Proceedings of the Zoological Society of London. (4); pp. 616-628 (crc00060)
Conservation: Pseudotropheus williamsi is evaluated by the international union for the conservation of nature in the iucn red list of threatened species as (NT) near threatened (2018).