Wagener's granulomatosis (WG) is a rheumatologic disease with unknown etiology which renal and pulmonary involvement is commonly seen. Renal involvement in Wagener's granulomatosis represents as a segmental necrotizing glomerulonephritis which is not visible with imaging techniques and usually presents with proteinuria, microhematuria, and hypertension. A rare presentation of the disease is a renal mass which can be mistaken as renal tumors, abscess, or lymphoma. We report a 22-year-old female with flank pain and fever who was admitted in our hospital. The patient underwent renal tumor biopsy and diagnosed with Wagener's granulomatosis in pathologic staining. The aim of this work is introduction of Wagener's granulomatosis as a differential diagnosis of renal tumors, to prevent unnecessary interventions and delayed treatment.