Appendix vermiformis duplex is an infrequent malformation. However if it is missed out, there might be some complications and medicolegal troubles. A surgeon must be aware of any other appendix during appendectomy. Therefore, the possible locations and shapes described in the Cave-Wallbridge classification should be considered by the surgeon. In this case report, we present a patient with a horseshoe-type dupplication of appendix in a perforated appendicitis diagnosed during an emergency laparotomy.