Tension hydrothorax, though rare, is a life-threatening complication of malignant pleural effusion (MPE). Early recognition and intervention are crucial to prevent hemodynamic instability and respiratory failure. We present a case of a 68-year-old woman with a history of breast cancer who presented with progressive dyspnea and significant weight loss, in addition to dextroposition of her heart on exam. Imaging revealed a large left-sided pleural effusion with pleural nodularity and displacement of both the heart and great vessels into the right hemithorax, consistent with tension hydrothorax from MPE. Management included immediate pleural drainage with tube thoracostomy, which led to symptomatic relief, and the diagnosis of MPE was later confirmed through pleural biopsy. This case highlights the importance of rapid diagnostic and therapeutic approaches in extreme and life-threatening presentations of MPE.