Abstract Introduction/Objective The unique morphologic and clinical features of neuroendocrine tumors have attracted the attention of physicians, most especially pathologists for more than a century. Neuroendocrine tumor of the duodenum is a rare entity and only accounts for ~ 2% of gastrointestinal neuroendocrine tumors. Though it was initially classified as duodenal gangliocytic paraganglioma due to the presence of sustentacular cells and its association with ganglion cells, it has now been reclassified in 2022 WHO classification as “composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET) due to its clinical features and immunophenotypic characteristics. Hence, we report a rare case of CoGNET in the duodenum. Methods/Case Report We present a 72-year-old female with a past medical history of hypothyroidism, hyperlipidemia, hypertension, deep vein thrombosis, and pulmonary embolism presenting with a 1-day history of abdominal pain and vomiting. Esophagogastroduodenoscopy (EGD) was performed, and it was concerning for a duodenal mass and the specimen was biopsied. Results (if a Case Study enter NA) The biopsy consisted of multiple tan-red hemorrhagic soft tissue, which on microscopic examination showed a triphasic histological pattern which includes neuroendocrine cells, spindle-shaped Schwannian/ sustentacular cells, and neuronal ganglion cells. Immunohistochemical stains performed showed the tumor cells are strongly positive for synaptophysin, and chromogranin; moderately positive with AE1/AE3, and patchy positive with S100. Desmin, CD117, DOG-1, CD34, and GATA were all negative in the tumor cells; the Ki-67 proliferative index was 1%. These morphological and immunophenotypic features are consistent with CoGNET. Conclusion CoGNET is a rare entity in the gastrointestinal tract especially in the duodenum and given its recent reclassification in 2022 WHO classification; pathologists, surgeons, and physicians need to be aware of such rare entities to improve patient care.