Arachnida evolved different reproductive strategies in the terrestrial habitats. Knowledge of the morphology of reproductive systems varies depending on the group, and for Opiliones only a few studies exists addressing this topic. Here, we describe the morphology of the male reproductive tract and the spermatozoon of the harvestman Mischonyx cuspidatus (Roewer, 1913). In this species, males have a single testis, a pair of deferent ducts, a seminal vesicle, a propelling organ and a penis. The lumen of the folded seminal vesicle and testis follicles are filled with spermatozoa, suggesting a storage of sperm related to a possible reproductive strategy involving multiple matings. The spermatozoa are aflagellate and ca. 6.5 µm in length. This study sheds light on the knowledge of the harvestman's reproductive biology and life strategy, which can be used in future studies involving Opiliones behavior and systematics.