Endometrial stromal sarcoma represents a very rare pathological entity occurring as a malignant disease in women genital sphere, frequently in the age group of 40-50 years. Low grade endometrial stromal sarcoma (LGESS) is a rare uterine sarcoma constituting 0.2% of all the uterine malignancies with a good prognosis despite a tendency to recur. We report a case of 42 yr old woman presented with menorrhagia, dysmenorrhoea, anemia and rapidly enlarging mass in uterus clinically diagnosed as leiomyoma, underwent a hysterectomy. Histological examination revealed cells with ovoid to short, spindle shaped nuclei resembling endometrial stromal cells proliferating in a space occupying manner and compressing and partially infiltrating the myometrium, rendered the diagnosis of LGESS. Our case emphasizes the inevitability for high index of skepticism and proper preoperative diagnosis in this rare tumor.