Primary appendiceal mucinous adenocarcinoma is a rare entity, while appendiceal carcinoma invading the urinary bladder is even rarer. The current study presents the case of a 54-year-old male with primary appendiceal mucinous adenocarcinoma, without gastrointestinal symptoms, presenting only with signs of bladder irritation. Abdominal computed tomography scans demonstrated a mass at the right anterior level of the bladder. During intraoperative exploration, the mass was detected to connect and adhere to the ileocecal junction, and normal appendix tissues were not found. The frozen section revealed a mucinous adenocarcinoma of the appendix and the patient immediately underwent a subsequent hemicolectomy. The present case indicates that a diagnosis of a primary appendiceal mucinous carcinoma must considered by radiologists and clinicians for patients who do not exhibit gastrointestinal symptoms, but show involvement of the nearest organs and the bladder wall.