Malignant pericardial effusion with cardiac tamponade is a rare manifestation of metastatic gynecological cancer. A 35-year-old female was diagnosed with clear cell adenocarcinoma of the vagina. Four years after partial vaginectomy, she developed regional recurrence and was treated with surgical excision followed by platinum-based chemotherapy and radiation therapy. Six years later, the patient was diagnosed with lung metastases and received a combination adriamycin and platinum-based chemotherapy. Shortly after completing treatment, she presented with weakness and was found to be hypotensive on physical exam. Computed tomography scan confirmed a pericardial effusion with evidence of bilateral heart failure. She underwent an emergent pericardiocentesis and eventual pericardial window procedure. Metastatic adenocarcinoma of the vagina can present with malignant pericardial effusion with cardiac tamponade. Therefore, gynecologists and gynecological oncologists need to be familiar with the diagnosis and management of this disease process.