Biliary mucinous cystadenomas (BMC) of the liver are rare benign cystic tumors, however an estimated 20% undergo malignant transformation. They have recently been redefined as mucinous cystic neoplasms in the 2010 WHO classification. The preferred treatment is through radical resection, as there are high recurrence rates with other treatment modalities; however this is often not possible in patients with bilobar or giant cysts, and liver transplantation may be indicated. We present a patient with a giant biliary mucinous cystadenoma of the liver and discuss the management with reference to the literature. A 47 year-old woman presented with a 6-week history of moderate epigastric discomfort on a background of 12 months of symptom-free abdominal distension. A giant cystic bilobar tumor of the liver measuring 22 x 23 x 17 cm was diagnosed and characterised by ultrasound scan and magnetic resonance imaging. Serum bilirubin, alkaline phosphatase and gamma-glutamyl transpeptidase were elevated, though other laboratory data including tumor markers (CEA, aFP, CA19-9) were within normal limits. Total excision of the cyst was not possible due to its size and position, and the patient underwent cyst drainage, a sub-total cyst excision and omentoplasty. Histology confirmed a benign biliary mucinous cystadenoma with an ovarian stroma. Though the patient remained clinically well, routine post-operative computed tomography (CT) surveillance showed an 11 cm recurrent cyst at 6 months. A partial cyst resection with close follow-up, regular CA19-9 serology and ultrasound/CT imaging, may be a reasonable alternative for bilobar or giant cysts. However should any features pathognomonic of malignancy develop, then a liver transplantation is indicated.