PURPOSE: A case of the rare, benign, Wilms' tumor (WT) variant, metanephric adenofibroma (MAF), is presented. MATERIALS AND METHODS: The patient is a 21-year-old female with an incidentally discovered enhancing renal mass. The diagnosis, workup and treatment are outlined. RESULTS: The 19 cm renal mass was ultimately resected via robot-assisted partial nephrectomy. Pathologic diagnosis at our institution was confirmed as a MAF by the National Wilms' Tumor Study Group (NWTSG). CONCLUSION: Difficult to differentiate from WT, it is imperative that MAF be recognized and appropriately diagnosed because unlike adult WT, the natural history of MAF is indolent and adjuvant chemo/radiation therapy is rarely necessary. This case reinforces the importance of review of potential WT variants by the NWTSG.