Xanthogranulomatosis is an idiopathic, rare process in which lipid-laden histiocytes may deposit in various locations in the body, which if systemic is called Erdheim-Chester disease. A rare case of isolated retroperitoneal, bilateral perinephric xanthogranulomatosis is reported. The diagnosis was suspected on cross-sectional imaging and was confirmed by CT-guided percutaneous core biopsy.