Mucoceles of the appendix are a rare group of lesions thought to occur as a sequelae of luminal obstruction as well as certain benign and malignant neoplasms of the appendix. Early, preoperative diagnosis is rare. We report a case of an appendiceal mucocele in which the diagnosis was suggested by computed tomographic imaging and colonoscopy, and confirmed at surgery. Radiologic, endoscopic, and pathologic correlations of this rare entity are discussed.