We report an unusual case of acute appendicitis caused by a mucinous cystadenoma of the cecum obstructing the lumen of the appendix. At laparoscopic appendectomy, an inflamed appendix was identified and resected. Subsequent histologic evaluation of the appendiceal base revealed mucin lakes. After discovery of a cecal mass at colonoscopy, the patient underwent definitive right hemicolectomy for treatment of a benign mucinous cystadenoma of the appendix.