We discuss a patient who had poorly differentiated HCC with pyrexia and high CRP in laboratory data, which are not commonly observed in the usual HCC. A 50-year-old man with a history of liver dysfunction was admitted with a chief complaint of a prolonged fever and general fatigue. Preoperative diagnosis was HCC with portal vein tumor thrombus. Posterior segmentectomy of the liver and thrombectomy was performed. Rapid tumor recurrence occurred after surgery, and he died 79 days after the operation. Immunohistochemical stain of HCC in this patient revealed the production of proinflammatory cytokine, interleukin-8 (IL-8). IL-8 production may have contributed to the high fever, high inflammatory reaction, and poor prognosis in this case.