Neuroblastoma (NB) is a common malignancy in children, but rarely occurs in adults. Accepted unfavorable prognostic factors include age over one year, low histological grade and advanced stage, MYCN amplification, chromosomal aberrations, elevations of neuron specific enolase and lactate dehydrogenase, and increased catecholamine metabolites in urine or serum. In adults, abdomen/retroperitoneum are the primary sites and in children the adrenal gland. We report a 38-year old civil servant who presented at our urology clinic on the 21st of December 2007 with a six month history of right flank dull pain which was worse on walking and relieved by rest, hypertension and a large right retroperitoneal mass. Tumor resection revealed a grade III NB. Chemotherapy using a combination of vincristine, adriamycin and cyclophosphamide was started. Follow-up showed regression of the mass initially with a relapse after patient absconded for three months. He resurfaced with new masses and he had a repeat chemotherapy with disappearance of the masses and is currently undergoing further treatment. To our knowledge this is the only report of NB in an adult registered so far in Nigeria and perhaps the whole of Africa. Currently, there are no standard treatment guidelines for patients with NB in adulthood. This study emphasizes the need for a standard treatment regime for adult onset neuroblastoma and its recognition as a possible differential in intra-abdominal mass in adults.