The combination of chemotherapy and immune checkpoint inhibition (ICI) therapy is the current standard of care for most patients who are fit to undergo treatment for metastatic NSCLC. With this combination, renal toxicity was slightly higher than with chemotherapy alone in initial clinical trials. However, in recent real-world data, loss of kidney function is reported to be more frequent. Both chemotherapy and ICI therapy can induce renal impairment, although the mechanism of renal damage is different. Renal injury from chemotherapy is often ascribed to acute tubular injury and necrosis, whereas the main mechanism of injury caused by ICI therapy is acute tubulointerstitial nephritis. In cases of concomitant use of chemotherapy and ICI therapy, distinguishing the cause of renal failure is a challenge. Discriminating between these two causes is of utmost importance, as it would help assess which drug can be safely continued and which drug must be halted. This review aims to describe the underlying mechanisms of the renal adverse effects caused by chemotherapy and ICI therapy, leading to a suggested diagnostic and treatment algorithm on the basis of clinical, laboratory, radiographic, and pathologic parameters. This algorithm could serve as a supportive tool for clinicians to diagnose the underlying cause of acute kidney injury in patients treated with the combination of chemotherapy and immunotherapy.