Retroperitoneal fibrosis (RPF) is a rare disease characterized by the presence of a retroperitoneal tissue, consisting of chronic inflammation and marked fibrosis, which often entraps the ureters or other abdominal organs. A 67-year old man presented with general weakness and oliguria. Laboratory findings showed blood urea nitrogen of 77.7mg/dL, serum creatinine of 9.24 mg/dL and IgG4 level was normal range. Computed tomography (CT) findings showed bilateral hydronephrosis and distal ureteral obstruction due to fibrotic adhesion to presacral mass. We performed percutaneous nephrostomy and hemodialysis. We performed laparoscopic biopsy which showed fibrosis with mild inflammation and degeneration of adipose tissue. We treated with prednisolone and tamoxifen and double J-catheter insertion. One month after, follow-up CT scan showed near resolution of hydronephrosis and reduction in the size of the retroperitoneal mass. We report a successful predinsolone and tamoxifen treated case of acute kidney injury occurring as focal retroperitoneal fibrosis.