Endometrial stromal sarcoma (ESS) is a rare and aggressive uterine malignancy that can often mimic other malignancies, including small cell carcinoma, both clinically and histologically. This case report presents a 55-year-old female who presented with post-menopausal bleeding and imaging findings suggestive of cervical carcinoma. Histopathological examination revealed a small round cell tumor, initially raising concern for small cell carcinoma. However, immunohistochemical markers such as BCOR and Ki67 were crucial in differentiating ESS from small cell carcinoma and other malignancies. Surgical resection was performed, confirming the diagnosis of ESS. This case emphasizes the importance of accurate diagnostic workup, including immunohistochemistry, in distinguishing ESS from other uterine tumors and guiding appropriate treatment.