We describe a successful treatment of a severe, persistent bleeding from both kidneys in a patient with autosomal dominant polycystic kidney disease (ADPKD) with tranexamic acid (TXA), a potent antifibrinolytic agent. The bleeding could not be controlled by intensive conservative treatment, it became life-threatening and urgent bilateral nephrectomy was intended. Since local and systemic hyperfibrinolysis play a role in bleeding in ADPKD patients, we tried TXA treatment. In fact, the massive bleeding promptly stopped, and haematuria gradually ceased. Removal of both kidneys was prevented. After 5 days both ureters became obstructed by blood clots, but placing J-catheters in each pyelon successfully solved this complication. Our case shows that it is reasonable to try antifibrinolytic treatment with TXA in such devastating uncontrolled bleeding.