Alpha-fetoprotein (AFP) is a tumor marker associated with liver cancer and non-seminomatous germ cell tumors. Wilms tumor (WT) is the most common pediatric renal cancer and the second most frequent childhood abdominal malignancy. The International Society of Pediatric Oncology does not routinely recommend pretreatment biopsy in children with suspected WT and the diagnosis is mainly clinical and radiological. We herein describe a pediatric case of suspected WT with atypically elevated serum AFP and clinical and radiological findings uncommon in WT, requiring pretreatment biopsy for a definitive diagnosis. Tumor histology confirmed a stage IV WT.