This species belongs to Hillia subg. Hillia, and is apparently pollinated by hawkmoths. This is the most widely distributed and the most commonly collected species in the genus. It is variable morphologically in particular in the Andes, and as circumscribed here may include more than one species. However no morphological characters are evident that clearly separate subgroups within the plants now included in this species.

The name Hillia tubiflora Cham. was long treated as a synonym of Hillia illustris, based on annotation by workers who saw the now-destroyed type collection at B (e.g., Taylor, 1994). However, further study shows that this specimen corresponds instead to Hillia parasitica in today's classification (L. Ball, pers. comm. XII 2022).