A 50-year-old female with a histologically-proven duodenal neuroendocrine tumor (d-NET) was referred to our hospital for further examination. Esophagogastroduodenoscopy revealed a reddened, hemispheric lesion in the anterior wall of the duodenal bulb. Magnifying endoscopy with narrow-band imaging showed dilatated vessels without variable calibers on the surface. Endoscopic ultrasonography confirmed a 6-mm hypoechoic lesion extending into the submucosa.