A primary neoplasm of the right adrenal gland in a 4-year-old boy was discovered after the patient developed bowel obstruction following an appendectomy. Until the histologic examination, the tumor was thought to be a neuroblastoma. However, the intra-adrenal tumor was composed of blastematous nodules, primitive tubules, and glomeruloid structures whose overall composition resembled a Wilms' tumor. Other than a single focus of mucinous glands, the tumor lacked the range of somatic tissue types of a teratoma. Approximately 50 cases of putative extrarenal Wilms' tumor have been reported. The retroperitoneum is one of the more common primary sites, yet our case is the first documented example of a neoplasm with features of a Wilms' tumor arising in the adrenal. Based on the embryologic and anatomic relationship between the adrenal gland and kidney, it is somewhat surprising that other instances of similar appearing tumors have not been described before the present case. Our patient was managed on a Wilms' tumor protocol and remains tumor free 15 months after surgery.