Tumor lysis syndrome (TLS) is an oncologic emergency due to massive tumor cell lysis with the release of large amounts of potassium, phosphate, and nucleic acids into the systemic circulation. Clinical presentation is characterized by hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia. Acute kidney injury due to tumor lysis is potentiated by the precipitation of uric acid and calcium phosphate as well as renal vasoconstriction. Early recognition of tumor lysis can help prevent cardiac arrhythmias, seizures, and death. Management includes intravenous hydration to maintain urine flow, medications targeting hyperuricemia including rasburicase and allopurinol and in severe cases renal replacement therapy may be required.