Primary ovarian leiomyosarcoma is a very rare tumour which is most commonly seen in postmenopausal women. A case is described here involving a 30-year-old female who presented with pain in the abdomen. The patient underwent laparotomy with peritoneal lavage, bilateral salpingo-oophorectomy, and total abdominal hysterectomy. Microscopic and immunohistochemical findings established the diagnosis of primary ovarian leiomyosarcoma. Similar to sarcoma of other tissues, an adjuvant chemotherapy regimen consisting of vincristine, epirubicin, and cyclophosphamide was given for this present case. Six months after treatment completion, the patient is on regular follow-up and disease-free on clinical and radiological examination.