It is considered to be the sister taxon to the genus Ahetulla, which it diverged from during the mid-Oligocene. Due to its age, Proahaetulla may be one of the oldest monotypic lineages of snakes to still persist in the Western Ghats. The study that described Proahaetulla also found that the clade containing it and Ahaetulla was a sister group to the genus Dryophiops. Proahaetulla is also the first deeply divergent snake genus to be described from the Western Ghats in over a century; numerous Indian snake species have had new genera created to reclassify them from the genera they were originally classified in, but Proahaetulla is completely new, possibly having never been encountered by science prior to its description as a new genus and species.