We report a rare case of large-cell neuroendocrine lung carcinoma exhibiting tumor lysis syndrome (TLS) while receiving chemotherapy and being successfully treated by rasburicase. A 70-year-old man was diagnosed with large-cell neuroendocrine carcinoma after being operated on for a left upper lung carcinoma. He had received adjuvant chemotherapy after the operation, but it resulted in a metastatic liver tumor. Five days after administration of amrubicin as the second-line chemotherapy, TLS occurred with an elevation of uric acid, potassium, and creatinine in serum. To elude the severe renal dysfunction, rasburicase was used in addition to the usual fluid therapy. The value of uric acid was remarkably decreased, and the renal function was improved after 3 days of rasburicase administration. Rasburicase thus might be useful for the initial treatment of TLS even in the clinical course of lung cancer.