Endometrial stromal sarcoma is a rare mesenchymal tumor with the potential for intravascular metastases. We present the case of a 52-year-old female patient with a history of previously resected endometrial sarcoma who was found to have an inferior vena cava thrombus with intracardiac extension. Pathological assessment following resection revealed intravascular extension of an underlying endometrial stromal sarcoma. This case demonstrates the aggressive nature and intracardiac metastatic potential of endometrial sarcomas.