A male in his 60s aware of an abdominal mass for 14 years but asymptomatic had not visited a medical institution. During a medical checkup, he was informed of his mass and admitted. Imaging revealed an upper abdomen 26-cm tumor with a mixture of cystic and substantial portions. A mixed-type pancreatic serous cystic neoplasm (SCN) was suspected; however, surgery was contraindicated due to common hepatic arterial penetration and varicose veins around the tumor. Regular follow-up was scheduled, but the patient experienced repeated bleeding from gastric varices six years later. Edoscopic hemostasis was ineffective. After a definitive SCN diagnosis by percutaneous tumor biopsy, the patient underwent endovascular treatment for hepatopatal gastric varices with abundant tumor blood flow. The left gastric vein was punctured under ultrasonographic guidance, and there was improvement following N-butyl-2-cyanoacrylate injection into embolized gastric varices. This is the first case report of a patient with an inoperably large SCN requiring percutaneous embolization of varicose veins.