Primary ovarian leiomyoma of the ovary is an extremely rare tumor; only approximately 70 cases have been reported worldwide [1]. The lesions are usually found incidentally, with the majority being discovered in perimenopausal and postmenopausal women (85%) [2,3]. They are difficult to diagnose preoperatively based on ultrasonographic results, because they are usually small in size (< 3 cm in diameter) and rarely induce serious clinical symptoms [1,3]. We present a case of asymptomatic primary leiomyoma of the left ovary of a pregnant woman. A 41-year-old woman, gravida 3, para 1, ectopic 1, had a history of a right tubal ectopic pregnancy, and a left ovarian echogenic mass measuring about 3.5 × 2.4 × 2.5 cm was observed using ultrasonography 1 year prior to this presentation. She received medical treatment with two doses of methotrexate, and the ectopic pregnancy had terminated at the 6-week follow-up examination (tested by β-hCG). Follow-up laboratory test results showed that CA-125 was within the reference range limits. Intrauterine pregnancy was noted 1 year after the ectopic pregnancy. The patient underwent an uneventful routine prenatal examination. On acute severe variable fetal distress during labor, the patient received emergency cesarean section and was delivered of a female infant weighing 2,930 g. During this procedure, the opportunity was taken to review the left ovary, and a fasciculated grey-white left ovarian tumor that was firm and solid measuring 4.5 × 4.4 × 3.2 cm, suggesting fibroma/thecoma or leiomyoma, was discovered, and a left oophorectomy was performed. No ascites fluid was noted in the abdomen. Following meticulous examination of the uterus, three small intramural leiomyomas of approximately 1 cm in diameter, were further discovered. The patient was discharged 5 days after surgery, and her recovery period was uneventful. The final histopathologic examination revealed ovarian leiomyoma. The mass consisted mostly of interacting