Information on the life history of European cave salamanders remains limited. Despite a handful of studies carried out both under natural and controlled conditions, one of the least known aspects concerns the reproductive and breeding behaviour. Here we present information on the breeding behaviour of all the eight European Hydromantes species collected during four years of intensive monitoring (2014–2017). We provide information on the breeding phenology, suggesting that the breeding seasons are likely linked to environmental variables. Nesting sites were used repeatedly in different years by different females. Our data indicated a seasonality of mating activity and the possibility of sperm storage. Furthermore, we report on the presence of a single large-sized oviductal egg in H. imperialis. Finally, we documented oviparity in Hydromantes sarrabusensis, the only species that was suggested to be viviparous.