Anaplastic sarcoma of the kidney is an extremely rare tumor, mostly observed in pediatric age group. This tumor is the counterpart of embryonal or undifferentiated sarcoma of the liver and pleuropulmonary blastoma of lung. To the best of the authors' knowledge, only 26 cases were reported in the English literature and the current case, a 3-year-old male, was the 27th reported case with this tumor. It is very important to differentiate this tumor from the Wilm tumor as well as renal cell carcinoma, as they were preoperative diagnosed in all of the reported cases.