We present a case with cardiac metastasis of the great saphenous vein leiomyosarcoma (LMS) that presented to the emergency department with dyspnea and palpitations 2 months ago. In this patient, hemodynamic instability was caused by an extensive right ventricular cavity and outflow tract invasion of the LMS. Treatment of the patient included incomplete mass resection, adjuvant chemotherapy, and permanent pacemaker implantation (due to postoperative complete atrio-ventricular block).