We report a case of pleomorphic sarcoma in a 42-year-old man with adult polycystic kidney disease [APKD]. Abdominal ultrasonography, computed tomography and MRI scans have revealed heterogenous bilateral renal cysts with a voluminous mass in the upper pole left kidney. Radical left nephrectomy with histopathologic and immunohistologic examination have confirmed the diagnosis of pleomorphic sarcoma. Sarcoma associated with adult polycystic kidney disease is extremely rare and does not have particular radiological or biological features when compared to primary renal sarcoma.