Hanssuesia based on material originally named Troodon sternbergi by Barnum Brown and Erich Maren Schlaikjer in 1943. Later, it was transferred to Stegoceras as S. sternbergi by Williamson and Carr, 2002 and by Ryan and Evans, 2005. The genus was first named by Robert M. Sullivan in 2003 and the type species is Hanssuesia sternbergi. H. sternbergi is known from 7 specimens (mainly from frontoparietals) which were collected from two formations of the Belly River Group of Alberta, Canada, the Dinosaur Park Formation (late Campanian, 76.5–75 ma) in the Dinosaur Provincial Park, and the Oldman Formation (middle Campanian, 77.5-76.5 ma), as well as from the upper Judith River Formation of Montana, USA (late Campanian, 76–75 ma).
Like other pachycephalosaurs, Hanssuesia had a thick skull roof. However, Hanssuesia is distinguished from other pachycephalosaurs by having a depressed parietal region, wide frontoparietal dome, broad nasal characteristics, reduced prefontal lobes, and a reduced parietosquamosal shelf.