Although millipedes (Diplopoda) represent one of the most diverse classes of arthropods, data concerning details of their mating behaviour are very scarce. In this work, we explored mating behaviour of the European millipede Pachyiulus hungaricus under laboratory conditions, and its relationship with the size and shape of certain morphological traits. We conducted 3 types of behavioural tests: a mating arena test, a female choice test, and a male choice test. Premating behaviour was "sequenced" in 5 behavioural steps and, together with the duration of copulation, scored in all mating assays. Males were the more active sex in searching for mates, while females were the "choosier" sex. Furthermore, in the choice tests, previous mating partners had significantly more copulations than new ones, thus raising questions about postcopulatory sexual selection in this species. On the other hand, our results indicate that size and/or shape of the tested morphological traits, except for the shape of the male walking legs, were not subject to precopulatory sexual selection. Other sensory domains known to influence courtship behaviour need to be investigated in this regard in P. hungaricus.