Peripheral primitive neuroectodermal tumor (PNET) is a small round tumor belonging to the PNET/Ewing's sarcoma family classified based on location in the body. There have been a small number of case reports of PNET arising in the ovary. We present extremely rare case of PNET of the ovary occurring in a 32-year-old pregnant woman, which was detected during her second Cesarean section. She had a past history of oophorectomy due to a huge mature solid teratoma in left ovary during her first Cesarean section. She got the operation of right salpingoophorectomy during the second Cesarean section at local gynecologic clinic and referred to our institute. Magnetic resonance imaging and positron emission tomography revealed the PNET was metastased to the peritoneum and the lymph nodes. We had persecuted vincristine, doxorubicin, cyclophosphamide, and etoposide/ifosfamide 8 cycles. There has been no evidence of local tumor recurrence and metastasis after the chemotherapy until now.