Mucin-producing bile duct tumor is a rare biliary tract tumor. Despite the development of modern diagnostic technologies such as ultrasonography, and angiography, the precise determination of this tumor is difficult because of ambiguity caused by the abundant mucin secreted by the tumor and/or by the superficial mucosal spread of the tumor along the bile duct. Given these problems, selective percutaneous transhepatic biliary drainage (PTBD) and percutaneous transhepatic cholangioscopy (PTCS) are indispensable for the accuracy staging of this cancer. But, PTCS has a risk of a rare but serous complications, seeding metastasis at the sinus tract of PTBD, whereas the retrograde approach minimizes this risk. We report the case of a patient who underwent the successful resection of a mucin-producing bile duct tumor. The tumor was diagnosed preoperatively as originating in the left caudate lobe after ERC and peroral cholangioscopy (POCS).