Pulmonary hypertension is commonly seen with multiple complex disorders managed in the intensive care unit. Common causes of pulmonary hypertension in critically ill patients include severe hypoxia, sepsis, left ventricular failure, massive pulmonary emboli, drugs, and worsening of chronic pulmonary hypertension, among others. Reversible pulmonary hypertension is rare and it has been reported with mediastinal involvement of sarcoidosis and in critically ill patients with severe acute chest syndrome. We present a 43-year-old male who was admitted with acute-onset shortness of breath. A massive right-sided pleural effusion and left-sided pneumonia was found on chest roentgenogram. Echocardiogram showed severe pulmonary hypertension with normal left ventricular function. Patient was treated for presumptive pneumonia and underwent pleural fluid drainage. An echocardiogram repeated after removal of pleural fluid showed resolution of pulmonary hypertension. We hypothesize that the large pleural effusion produced mechanical compression of mediastinal and pulmonary vessels leading to severe pulmonary hypertension, which reversed upon drainage of pleural effusion. This has both diagnostic and management implications.