We report a case of mucinous carcinoma of the pancreas, a rare invasive carcinoma of the pancreas. A 69-year-old woman was admitted to our hospital due to a huge duodenal tumor. An esophagogastric duodenoscopy revealed a 10 cm tumor with surface irregularity and a high amount of mucus in the second and third portions of the duodenum. Contrast-enhanced ultrasonography（CE-US）and computed tomography（CT）showed the mass to be located in the pancreatic head, recognizable as enhanced parts of the edge and the septum. Moreover, CE-US revealed dendritic enhancement in the lesion. Magnetic resonance imaging（MRI）showed low-, high-, and relatively high-intensity masses on T1- and T2-weighted images and magnetic resonance cholangiopancreatography（MRCP）．Positron emission tomography-CT showed high fluorodeoxyglucose integration in the part of the tumor. As no metastatic lesion could be detected, a pylorus-preserving pancreaticoduodenectomy was performed. A final pathological diagnosis of mucinous carcinoma was made. CE-US, MRI, and MRCP may be useful for the diagnosis of mucinous carcinoma of the pancreas.