 Introduction, immune checkpoint inhibitors, CPIs, represent novel new cancer immunotherapy agents. The use of Nivellumab has been linked with immune-mediated acute interstitial mephritis, AIN. Case presentation, we present the case of a patients with recurrent hepatocellular carcinoma who developed severe Fankoni syndrome, as evidenced by hyperchloremic metabolic acidosis, hypokalemia, hypophosphatemia, glucosuria, amino aciduria, eight months after initiating treatment with Nivellumab without any evidence of acute renal insufficiency. Conclusion, clinicians need to be aware of the renal side effects of new novel cancer immunotherapy agents, such as immune CPIs. This article was authored by Muhammad Tanawi and Bahar Bestani.