A 65-year-old woman was suspected of having advanced gallbladder cancer based on imaging results. This was considered inoperable because it was accompanied by possible liver metastasis. To confirm the diagnosis prior to chemotherapy, endoscopic transpapillary catheterization in the gallbladder (ETCG) was performed. The bile cytology was analyzed by the cell block method, which revealed mixed adenoneuroendocrine carcinoma. Based on the cytological results, extended cholecystectomy and partial hepatectomy were performed for the metastatic lesions. Bile cytology by ETCG with the cell block method was useful for deciding the therapeutic strategy in this patient with metastatic gallbladder cancer.