Introduction. Ganglioneuroblastoma is a rare peripheral neuroblastic tumor that is derived from developing neuronal cells of the sympathetic nervous system, and is found mostly, but not exclusively, in babies and young children. Case presentation. To the best of our knowledge, there have been no previously reported cases of ganglioneuroblastoma of the mediastinum from Pakistan. We present a case of ganglioneuroblastoma in an eight-year-old Pakistani Sindhi boy incidentally found to have a large posterior mediastinal mass that on biopsy initially looked like ganglioneuroma. He underwent successful excision of the mediastinal mass and remained stable post-operatively. Final pathology findings showed a ganglioneuroblastoma. He has remained free of symptoms on long-term follow-up. Conclusions: The rarity of this tumor along with its almost exclusive occurrence in the pediatric population necessitates a thorough investigation of patients presenting with a symptomatic mass.