We present a rare case of hepatobiliary cystadenocarcinoma with biliary communication. A 74-year-old woman had a liver cyst that had enlarged from 5 cm to 8 cm in diameter over the last 2 years. A mural nodule, 1 cm in diameter, was first demonstrated by computed tomography in a multilocular cyst in segment IV. The nodule showed hypervascularity at angiography and computed tomography during arteriography. Percutaneous transhepatic cystography demonstrated a communication between the cyst and the biliary tract. The cyst was filled with mucinous and gelatinous fluid and was revealed to contain cancer cells. The patient underwent total tumor extirpation with the surrounding hepatic parenchyma. We confirmed and closed the biliary fistula connected to the right hepatic duct. Histologically, the cyst wall was composed of cystadenoma and the mural nodule showed in situ papillary adenocarcinoma. The patient is doing well 9 months after surgery. Complete tumor extirpation and closing of the biliary fistula is the treatment of choice.