A patient showed signs of fever and Hemovac insertion site discharge 8 days after surgery and was admitted. Abdominal paracentesis found milky ascites with triglyceride levels of the peritoneal fluid as high as 1,603 g/mL. Diagnosed as chylous ascites, symptomatic therapy such as empirical antibodies and diuretics was administered with paracentesis before being discharged. The ascites volume increased again, and the patient was re-admitted. The patient was treated with orlistat, octreotide, total parenteral nutrition administration, ascites drainage, and diuretics. Ascites levels increased further and intraperitoneal Viscum was administered. Clear ascites was observed, and the patient was discharged. We reported a case where conventional treatment for chylous ascites that occurred after pancreaticoduodenectomy was shown to be ineffective while Viscum extracted from mistletoe was able to manage chylous ascites.