The occurrence of mucinous cystadenomas localized to the liver and pancreas simultaneously and treated with a single surgical procedure has been described for the first time in this report. A 47-year-old woman attended the outpatient clinic complaining of abdominal pain and the appearance of an abdominal mass. On clinical examination, hepatomegaly was found. An abdominal computed tomography scan showed a large cystic lesion of the left lobe of the liver, thus causing the hepatomegaly. Moreover, the computed tomography scan showed a cystic lesion of the pancreas. Both lesions had thick walls and septa. Magnetic resonance imaging of the liver and pancreas confirmed the presence of septa within the cysts. Surgery was performed owing to the suspected malignancy. It should be emphasized that the patient had preoperatively received prophylactic treatment for hydatosis. A hepatic pericystectomy and enucleation of the pancreatic lesion were performed during the surgery. Pathology showed a mucinous cystadenoma without sign of malignancy. At the 4-year follow-up, no recurrence was found. This case is of interest for several reasons: the unusual double presentation, the treatment, and the follow-up. This case report confirms the common origin of mucinous cystic tumours of liver and pancreas.