Adenocarcinoma is the most common type of colorectal neoplasia associated with chronic inflammatory bowel disease (IBD), but other types of epithelial and non-epithelial tumors have also been described on the inflamed bowel; among others, neuroendocrine tumors (NETs) which are rare tumors. We report the case of a patient admitted to the emergency department for an acute colitis inaugurated by ulcerative colitis (UC) and in whom a NET of the appendix was discovered on the colonic resection specimen. The prevalence of NETs in IBD patients is high in the literature. Their discovery is most often incidental. The presence of a significant number of neuroendocrine cells in the inflamed mucosa suggests that chronic inflammation is responsible for the development of this type of neoplasia.