Radiofrequency ablation is a safe and effective treatment for small primary or secondary liver tumors. Development of new probes has allowed the use of radiofrequency ablation for ablation of tumors > 5 cm in the liver. We present a case of acute intravascular hemolysis and hemoglobinuria during radiofrequency ablation of a large 8-cm hepatocellular carcinoma via laparotomy. The hemolysis was recognized during the operation by change of urine color, and prompt management was initiated to prevent acute renal failure. Literature search revealed that radiofrequency ablation can induce hemolysis in experimental setting, but this is the first clinical report of acute hemolysis during radiofrequency ablation for liver tumors.