BACKGROUND Inflammatory bowel disease (IBD) is a chronic, potentially life-long, disorder, including ulcerative colitis (UC) and Crohn’s disease (CD). Ulcerative colitis (UC) is an idiopathic chronic inflammatory disorder affecting the mucosa of the colon; it starts at the rectum and continues proximally in a continuous pattern to include up to the entire colon, called pancolitis. Patients with ulcerative colitis are at particularly higher risk of developing colorectal cancer (CRC) than the general population. Adenocarcinoma is the most common type of colorectal malignancy reported in the general population and IBD patients. One of the rarest types reported are the neuroendocrine neoplasms (NENs), which account for only 1% of all colorectal cancers, and it is very infrequent in IBD patients. Moreover, mixed neuroendocrine/non-neuroendocrine neoplasm (MiNEN) is a rare aggressive subtype of NENs that involves the colon in the background of an underlying chronic inflammatory process. CASE REPORT A 57-year-old woman, known to have long-term cirrhosis and ulcerative colitis, came to the Emergency Department with a suspected large-bowel obstruction. Imaging (CT scan of the abdomen) showed an obstructive transverse colon mass along with multiple descending colon masses. Biopsy of the transverse tumor confirmed the diagnosis of mixed neuroendocrine/non-neuroendocrine neoplasm (MiNEN). CONCLUSIONS Although neuroendocrine tumors are rare, strong association exist between MiNENs and ulcerative colitis. Further studies and reports can help better understand the pathogenesis, diagnosis, management, and prognosis of these cases.