Onco-nephrology focuses on the care of patients with cancer and kidney disease. Patients with acute kidney injury, tumor lysis syndrome, and malignancy-associated hypercalcemia are frequently treated in a critical care setting. Oncological emergencies can have a high mortality rate when not promptly recognized and appropriately treated. The critical care nurse should be knowledgeable regarding the risk factors, clinical manifestations, and laboratory abnormalities of common renal manifestations of malignancy and oncological emergencies to optimize care and improve patient outcomes.