Gangliocytic paragangliomas are rare benign neuroendocrine tumors that arise mainly in the duodenum. A total of 3 cases of duodenal gangliocytic paraganglioma have been reported in Korea. The authors encountered another case of a gangliocytic paraganglioma in the duodenum. A 48-year old man presented with a mass in the duodenum that had been found incidentally in a medical checkup. The endoscopic examination revealed a 3.5x2.2 cm sized polypoid mass in the second portion of the duodenum. The patient underwent a polypectomy in the form of a wedge resection under general anesthesia. Microscopically, the tumor was composed of epithelial cells forming paraganglioma like patterns, spindle cells and ganglion cells. Gangliocytic paragangliomas are believed to be benign tumors but regional lymph node metastasis and recurrence can occur in rare cases. During the 27-month follow-up after treatment, there was no evidence of recurrence or lymph node metastasis. We report this case to help improve the understanding of this rare disease.