Congenital renal anomalies are one of the most common congenital malformations. Supernumerary kidney is rare among these anomalies. A 78-year-old female patient, without urinary system complaints, was screened by abdominal computed tomography for staging of endometrial cancer. A supernumerary kidney fusing with the upper pole of right kidney was detected. Accessory kidney was located superomedial to the right kidney and was smaller than the normal kidney but there was no other pathology. In asymptomatic cases, follow-up is recommended due to increased risk of malignancy, for this reason, accurate diagnosis and follow-up are important.