Duplication cysts of the alimentary tract are uncommon congenital lesions that can occur anywhere along the path between the oral cavity and the anus, with a reported incidence of 1 in 20,000. Treatment is dependent upon the patient's age, whether the lesion is cystic, tubular, or in communication with the true intestinal lumen, and whether one or more anatomic locations are involved. Duplication cysts are diagnosed most frequently in children younger than 2 years. In the current study, we report a case of duodenal duplication cyst in an adult female that was removable by laparoscopy. Whereas the preoperative diagnosis was an ovarian endometriotic cyst that was later classified as endometriotic cyst of the supernumerary ovary during surgery, postoperative histological diagnosis revealed a duplication cyst of the alimentary tract. Because duplication cysts usually share a common wall as well as a common blood supply with the normal intestine, the adjacent bowel segment must also be removed along with the cysts. In this particular case, the common blood supply between the cyst and normal intestine was minimal, and there was no luminal communication with the adjacent intestine. It was therefore possible for a safe resection of the cyst to be done using laparoscopy without necessitating a bowel resection.