Onco-nephrology is a new and evolving subspecialized area in nephrology that deals with kidney diseases in cancer patients. As many newer cancer therapies emerge in the field of oncology, cancer patients are surviving longer than ever before. However, the benefits of the remarkable advances in cancer management have not been fully appreciated. Not only is cancer often associated with abnormalities that affect the kidney, but cancer therapy often leads to both acute and chronic kidney diseases. The development of cancer-associated kidney complications is associated with poor prognosis, whereas prompt recognition and treatment initiation are associated with improved outcomes in this population. Therefore, both nephrologists and oncologists should be familiar with the diagnosis and management of cancer-associated kidney complications. Another unique aspect of onco-nephrology is that significant improvements in predialysis and dialysis care in recent years have led to prolonged survival and a higher incidence of patients with chronic kidney disease suffering from cancer. Therefore, research is urgently needed to establish treatment for patients with chronic kidney disease. This update addresses the pathophysiology and treatment of various cancer-associated kidney complications, and highlights cancer treatment for patients with chronic kidney disease.