Endometrial stromal sarcoma (ESS) is a rare malignant tumor of the endometrium, occurring in the age group of 40–50 years. We report a case of low-grade ESS in a 39-year-old woman, presenting as rapid enlargement of a uterine fibroid polyp associated with irregular and excessive vaginal bleeding. Polypectomy followed by pan hysterectomy was performed. Histopathological examination and immunohistochemistry confirmed LGESS. As the tumor is rarely encountered, management protocols are still questionable. In our case, we tried a different post-surgical protocol and the patient is being closely followed up. Although rare, ESS should be considered in the differential diagnosis of all women who present with a rapid enlargement of a uterine leiomyoma.