Echinococcus granulosus is considered the major cause of human hydatid cysts. Usually the duration of cyst formation is 10-20 years. This period shortens significantly upon rupture of a primary cyst. The literature describes low incidence of primary involvement of ovary as a site of hydatid cyst formation. Our case is the first report on ovarian hydatid cyst in Iran. A 60-year-old woman was presented with abdominal pain in the left lower quadrant area. Paraclinical data were suggestive of neoplasia and preoperative diagnosis was ovarian tumor. During laparotomy, multiple cysts resembling hydatid cysts were observed in the left ovary. Pathological examination confirmed the diagnosis of hydatid cyst. Although there is a small possibility of secondary ovarian echinococcal disease, it is more probable for this case to be primary infection, as the patient had developed ovarian hydatid cysts 15 years after hepatic involvement and recurrence after 30 months is very uncommon.