Ganglioneuroma, which rarely occurs in the neck region, is a well-differentiated benign tumor of the sympathetic nervous system. A 39-year-old man presented with neck swelling for a year. A giant tumor was located on the left side of the neck. Schwannoma was suspected on preoperative cytology and core needle biopsy, and the postoperative diagnosis on pathological examination was ganglioneuroma. The origin of the tumor was considered to be the sympathetic nervous system based on the postoperative appearance of Horner’s syndrome. The treatment choice for ganglioneuromas is complete surgical resection, contrary to the nerve-sparing resection of schwannomas. Therefore, making the definitive diagnosis before surgical resection could be important. In this report, we focus on the differential diagnosis obtained with radiological findings and the treatment strategy for the tumor with a literature review.