Appendiceal mucocele is a cystic dilatation of the appendix due to abnormal appendiceal mucinous secretion. Cystadenoma of the appendix is one of the most common causes and is encountered in 0.6% of all appendectomy specimens. The diagnosis may be difficult due to the asymptomatic nature of the disease; pain in the right lower quadrant may be the only symptom. Complex ovarian cyst, urolithiasis or cystic hydatid disease of the liver have been reported as mimicking appendiceal mucocele in the literature. In this study, we present a case of mucinous cystadenoma of the appendix mimicking retroperitoneal hydatid cyst in a 59-year-old woman. The patient was treated with laparoscopic appendectomy with partial resection of the caecum following laparoscopic exploration.