Appendicular diverticulosis is a rare condition observed in about 0.004–2% of all appendectomy specimens. Risk of perforation/bleeding is high and a relevant association with mucinous neoplasms is known. Appendectomy is indicated even in case of occasional finding. We present the case of a 22-year-old man who entered the Emergency Room for pain in right iliac fossa. Blood tests showed only a slight increase in C-reactive protein. Abdominal ultrasound (US) evidenced an appendix with thickened walls and a rounded fluid-filled hypoechoic lesion at its distal tip. Laparoscopic appendectomy confirmed the presence of mucocele. Postoperative course was uneventful and the patients discharged on postoperative day 3. Histological examination indicated diverticulitis/peridiverticulitis of the appendix and acute suppurative appendicitis. No perforation of the diverticula was detected. No neoplastic epithelium/mucous material was observed. In our case, preoperative US proved to be a useful alternative to computed tomography for the diagnosis.