Background Focal segmental glomerulosclerosis (FSGS) is the most common primary glomerular disorder leading to end-stage kidney disease. The main pathophysiology of FSGS is “podocytopathies”, where podocyte injury leads to podocyte foot process. Pembrolizumab is an anti-programmed death 1 (PD-1) IgG4 antibody approved in advanced melanoma and non-small cell lung cancer which is one of the immune checkpoint inhibitors and can cause various immune-related renal adverse events including acute kidney injury. Several cases of anti PD-1 therapy induced glomerulonephritis have been reported so far, but FSGS has seldom been reported.   Case report 46-year old woman visited to Pusan National University Hospital with generalized edema which started a month ago. At June 21st of 2019, she was diagnosed with malignant melanoma on left posterior side of thigh and underwent wide excision surgery at May 2019. Because of the metastasis to left sentinel and inguinal lymph nodes, pembrolizumab was treated for 1 year from July 2019 to July 2020. Four months after the treatment, generalized edema occurred and gradually worsened with high blood pressure. Laboratory findings were as follows: total protein 5.71g/dL, albumin 2.84g/dL, creatinine 0.66mg/dL, urine red blood cells 6-10cells/high power field and urine protein to creatinine ratio (PCR) 3277mg/g. Kidney biopsy showed 2 glomeruli up to 36 glomeruli exhibiting segmental sclerosis with atrophied tubules and fibrosis and wide effacement of epithelial cell foot processes. After other etiological factors of secondary FSGS were ruled out, she was diagnosed with FSGS caused by pembrolizumab. According to the American society of clinical oncology practice guideline, she was treated with irbesartan and furosemide. After 2 months, the urine PCR decreased to 204mg/g.   Conclusion Glomerulonephritis can occur by PD-1 inhibitor as one of the renal immune related adverse effects. We encountered a rare case of FSGS caused by pembrolizumab.