Appendiceal mucocele is an infrequent but well recognized entity that can present with a variety of clinical syndromes or can be asymptomatic and discovered incidentally. A 55 years old patient was admitted in the emergency department for acute right lower quadrant pain. A diagnosis of appendicitis was made. At operation an appendiceal mucocele was found. An appendectomy was performed. The diagnosis of appendiceal mucocele is an important one in that it can be associated with malignancies and other serious gastrointestinal, ovarian, and urological complications.