Pulmonary arterial hypertension is a progressive, debilitating disease caused by a dysregulation of the pulmonary vascular tone that inevitably leads to right heart failure and death without treatment. Until relatively recently, the treatment options for those afflicted by pulmonary arterial hypertension were limited; today, a greater understanding of the pathophysiology behind this disease has led to several evidence-based therapies that can improve pulmonary function and quality of life for these patients. One of the primary mediators of pulmonary vascular tone is endothelin-1, which is a potent and long-lasting vasoconstrictor. Macitentan is a second-generation endothelin receptor antagonist that acts selectively as a pulmonary vasodilator without the significant side effects noted with previous endothelin receptor antagonists. This review focuses on the mechanism of action and pharmacokinetics of macitentan, as well as the adverse effects, efficacy, and clinical uses of macitentan in the clinical trials to date. In addition, the authors briefly review clinical trials currently underway to illustrate possible future directions for the use of macitentan.