Omental pregnancy is a very rare form of ectopic pregnancy. Here we presented a case of primary omental pregnancy diagnosed at surgical exploration. A 28 year old woman submitted with severe abdominal pain, without any delay of menstruation. History of the patient revealed no use of contraceptive method. There was no gestational sac in the endometrial cavity and no tubal ring in the adnexa, but free peritoneal fluid in the pouch of Douglas was detected at ultrasonography. Laparotomy was done according to pre-operative diagnosis of ruptured tubal pregnancy. Bilateral tubes and ovaries were intact; omental pregnancy was detected and partial omentectomy was performed. Although 16 cases of omental pregnancy (mostly secondary) were reported in the literature, herein we describe a primary omental pregnancy without adnexial involvement.