Case Description- On 23 July 2007, a four-years-old ewe, was referred to Veterinary Clinic of Tabriz Islamic Azad University. The clinical examination revealed lethargy, weight loss and hematuria in clinical examination. Left kidney in external palpation was painful, enlarged and abnormal. Treatment and Outcome- Laparotomy was done for exploratory diagnosis. In laparotomy the left kidney was obviously tumoral. Inspection of abdominal viscera revealed no abnormality. Unilateral nephrectomy was carried out on this animal by local anesthesia after sedation. Histologically, we diagnosed a renal cell carcinoma. Clinical Relevance- As clinical signs of renal cell carcinomas described in humans may or may not be present in domestic and laboratory animal species the only way to find out if a mass is a tumor, could be by doing an exploratory laparatomy, with a biopsy and histological examination. This is an easy procedure that can be performed on a sedated sheep with the help of local anesthesia. We propose radical nephrectomy to the treatment of choice for nonmetstatic renal cell carcinoma.