Retaining the etiology of a cystic lesion in the right iliac fossa can be difficult. Appendicular hydatid cyst is a very uncommon cause of a such lesion. In some cases, diagnosis is not obvious. It can radiologically mimic an appendix mucocele, a complicated ovarian cyst, an appendicular lymphangioma or an abscess. Our case highlights the difficulties encountered in this kind of situation and despite the contribution of imaging. We present a case of a 75 years-old woman presented with a right lower quadrant continuous pain. Abdominal CT-scan revealed a multilocular cystic and hydro-aeric mass. The diagnosis of an appendiceal mucocele complicated with gelatinous peritonitis was suspected. An open debulking surgery with right hemicolectomy was performed. The pathological exam has concluded to an infected appendicular hydatid cyst with thick calcified walls. The aim of this work is to report a case of an appendicular hydatid cyst that has imitated an appendicular mucocele to discuss the importance of differential diagnostic reflections and the appropriate treatment.