A 52-year-old woman was admitted to our hospital with right upper quadrant pain with gallbladder wall thickening and multiple liver tumors. Endoscopic ultrasound-guided biopsy revealed small cell carcinomas of both the gallbladder and liver. After 10 cycles of chemotherapy with etoposide and cisplatin, marked shrinkage of the tumors was evident on computed tomography. The patient subsequently underwent hepatectomy and resection of the extrahepatic bile duct and gallbladder with curative intent. Although no viable tumor cells were found in the resected specimens, we confirmed phagocytosis of tumor cells killed by chemotherapy in the resected liver specimen. Therefore, we suspected that the patient had primary small cell carcinoma of the liver that had been successfully treated. This is a rare case of primary small cell carcinoma of the liver that showed pathological complete response to chemotherapy with etoposide and cisplatin.