We aimed to present a case of appendiceal mucocele whowas admitted with abdominal pain, operated under electiveconditions and found to have been spontaneously drained fromthe root of the appendix to the colon in surgical exploration.A 41-year-old male patient was admitted to the emergencydepartment with abdominal pain. In clinical examination;tenderness, rebound and defense in the lower right quadrantof abdomen and leucocytosis were detected. Computerizedtomography scan showed the appearance of a cystic dilatedappendix. After resolution of the physical examination findingsbased on the antibiotic treatment, we decided to performelective surgery. In surgical exploration, ileocecal resection wasperformed by determining the mucocele of the appendix thathad been spontaneously drained from the root of the appendixinto the cecum lumen. On the sixth day after the operation,he was discharged without complications. Histopathologicalexamination revealed high-grade appendiceal mucinousneoplasia. Our patient’s follow-up in the first year after thesurgery revealed no recurrence. The patient is disease-freeat the end of his first postoperative year. The mucocele ofthe appendix is a cystic neoplasia containing mucin and itsperforation during surgery may result in the development ofpseudomyxoma peritonei in the late period. In our case, thefact that the lesion was spontaneously drained into the lumenof the colon reduced the risk of the mucocele rupturing andspreading into the abdomen during surgery.