Wilms' tumor (nephroblastoma) is the most common intraabdominal tumor in children; its three primary components are blastemal, epithelial and stromal, with predominance of tri-phasic lesion. The tumor is rare in adults, in whom the Wilms' tumor accounts for less than 1%. The case presented here concerns a case of 46-year-old female with stage II, Wilms' tumor, composed of purely mono-phasic differentiated epithelial component with favorable histology. The patient received radical nephrectomy, than post-operative chemotherapy and radiotherapy as recommended by National Wilms' Tumor Study. With the advent of modern chemotherapy, the adult Wilms' tumor can have a better prognosis than previously. Because of the rarity of adult Wilms' tumor and its unusual histo-morphology, this case is described and the literature, reviewed.