Neuroblastoma is an embryonic tumor of the sympathetic nervous system originating from neural crest cell remnants, which may be found in the adrenal glands or sympathetic chain. We report a case of a three-year-old girl who presented with flaccid paraparesis, and acute respiratory distress that required mechanical ventilation after a multiple-day history of gradual-onset dyspnea and right upper-lung opacity that was initially misdiagnosed as pneumonia. Chest and spinal magnetic resonance imaging (MRI) revealed a tumor in the posterior mediastinum with intra-spinal canal extension. The patient underwent thoracotomy and surgical en bloc resection with spinal canal decompression. Histopathology revealed neuroblastoma. The postoperative period was uneventful. The patient was administered a course of chemotherapy but died due to advanced stage tumor, severe pancytopenia, and septicemia with renal failure. The aim of this report is to consider posterior mediastinal neuroblastoma in the differential diagnosis of dyspnea and acute lower limb weakness in young children.