Development of direct-acting antiviral agents against hepatitis C virus (HCV) has changed the management of chronic HCV infection. We report three cases of newly diagnosed or exacerbated pulmonary arterial hypertension (PAH) in patients treated with sofosbuvir. All patients had PAH-associated comorbidities (HIV coinfection in two, portal hypertension in one) and one was already being treated for PAH. At admission, all patients presented with syncope, World Health Organization functional class IV, right-sided heart failure, and extremely severe hemodynamic parameters. After specific PAH therapy, the clinical and hemodynamic properties for all patients were improved. Severity and acuteness of PAH, as well as chronology, could suggest a causal link between HCV treatment and PAH onset. We hypothesize that suppression of HCV replication promotes a decrease in vasodilatory inflammatory mediators leading to worsening of underlying PAH. The current report suggests that sofosbuvir-based therapy may be associated with severe PAH.