Purpose: The aim of this study is to evaluate the safety of clinical usage of tadalafil in women with preeclampsia.Materials and methods: Maternal, fetal, and neonatal adverse events were closely examined in eight preeclampsia patients receiving tadalafil treatment.Results: There were no maternal adverse events associated with 10 mg/day of tadalafil. Even at 20 mg/day, only grade 1 headaches in two cases and grade 1 palpitation in one case were observed, which resolved spontaneously within 3 days. At a dose of 40 mg/day, there was only one case of grade 1 headache. All these adverse events were grade 1 and spontaneously resolved within 3 days. There were no fetal adverse events. All observed neonatal adverse events were thought to be caused by prematurity and not related to tadalafil.Conclusion: This study shows that tadalafil treatment for preeclampsia is deemed sufficiently tolerable. Although there was a dose-dependent increase in maternal adverse events, all the adverse events were mild and deemed to be safe for the mother and fetus at all dosages.