Immune checkpoint inhibitors (ICIs) such as anti-PD-1, anti-PD-L1 or anti-CTLA-4 have changed the treatment strategy especially in advanced malignancies. At the same time, ICIs have concerns about immune-related adverse events including acute kidney injury (AKI). We experienced a biopsy-proven ICIs-associated tubulointerstitial nephritis. 84 years old male patient who has non-small cell lung cancer with multiple systemic metastases was referred to a nephrology consultation for AKI. Pembrolizumab treatment began on June 1st, 2022. His baseline creatinine was 0.96mg/dL. AKI was developed after the 6th pembrolizumab administration, which was the 129th treatment day. Kidney biopsy was compatible with ICI-related acute tubular necrosis. He had a good appetite, no anemia, euvolemic state. None of the nephrotoxicant was found in his concurrent medication, except the proton pump inhibitor (PPI). After discontinuing PPI, serum creatinine normalized. The patient continued to maintain pembrolizumab during the whole evaluation period.