Chaga is a fungus in the family Hymenochaetaceae. It is parasitic on birch and other trees. Some people consider Chaga to be medicinal. Chaga mushroom is rich in a wide variety of vitamins, minerals, and nutrients. It has been reported that it suppresses cancer progression through anti-inflammatory and anti-oxidant effects. Nevertheless, in the recent report, Chaga mushroom can result in acute oxalate nephropathy. We report a case of acute oxalate nephropathy with nephrotic syndrome in a 69-year-old male, associated with the ingestion of Chaga mushroom powder (2-3 teaspoons per day) and vitamin C for past three months. He had acute kidney injury with clinical manifestations of nephrotic syndrome. Because his kidney function did not improve, he received hemodialysis and renal biopsy. Pathologic findings showed focal acute tubular injury, calcium oxalate crystals in tubules, interstitial fibrosis and tubular atrophy in light microscopy, and effacement of podocyte foot process in electron microscopy. High dose of steroid (intravenous hydrocortisone 500mg twice a day for 3 days and oral prednisolone 1mg/kg) was treated with hemodialysis. Finally, his kidney function recovered just one month after the start of treatment, and nephrotic syndrome was also remitted completely.