Vulvar leiomyosarcoma is a rare smooth muscle malignant neoplasm but it is the commonest type of vulvar sarcomas. It may mimic benign tumors and misdiagnosis could delay proper management. We report a case of a 38-year-old pregnant woman with leiomyosarcoma of the vulva. The patient presented to her primary general practitioner with a small vulvar mass that she had first noticed one year prior. The tumor was suspected to be benign Bartholin's cyst and treated with antibiotics. The patient declined improvement and had many consultations to different clinics where she had been diagnosed and treated the same. The tumor size started to grow rapidly after she got pregnant, and the patient was referred to our hospital where she underwent tumor resection. Histopathology revealed leiomyosarcoma. The patient had further assessment and close follow-up and has had no recurrence for 12 months. There is little literature available on vulvar leiomyosarcoma, most of which are case reports, and most gynecologic oncologists will go through their whole careers without seeing a single case.