We report a case of sarcomatoid carcinoma with components of small cell carcinoma and undifferentiated carcinoma of the gallbladder. An 84-year-old woman was admitted to our university hospital with right upper abdominal pain and back pain. Clinical diagnosis of a gallbladder tumor was made based on the findings of abdominal ultrasonography, computed tomography and endoscopic retrograde cholangiopancreatography, and a cholecystectomy was carried out. On gross examination a pedunculated polypoid tumor protruded into the lumen of the gallbladder. Histologically the tumor was composed of carcinomatous and sarcomatous components; the carcinomatous component consisted mainly of small cell carcinoma and undifferentiated carcinoma. In general, the carcinomatous component of sarcomatoid carcinoma of the gallbladder consists of adenocarcinoma, and there have only been two previously reported cases in which the carcinomatous component consisted of small cell carcinoma or undifferentiated carcinoma. Because the patient's prognosis may be influenced by the peculiar carcinomatous component in such cases, it is important to accumulate case reports that clarify their clinicopathological features.