A case of extensive ganglioneuromatosis (GN) of gallbladder is presented. A 38-year-old man presented with a hepatic hilar mass (Ø ~ 48 mm) and gall stones. He had undergone total thyroidectomy for medullary thyroid carcinoma 8 years earlier. The hepatic hilus tumor, which had been clinically suspected to be a lymph node metastasis from the medullary thyroid carcinoma, was found to be pheochromocytoma. The gallbladder, resected with a clinical diagnosis of cholelithiasis, showed extensive transmural GN despite a grossly normal appearance. Taking into account the past history, the patient was diagnosed as having multiple endocrine neoplasia 2b (MEN2b)-associated GN of gallbladder and ectopic pheochromocytoma. As GN of gallbladder in MEN2b has been rarely reported, the histological findings are described in detail and a brief review of literature is carried out.