Since the coronavirus disease 2019 (COVID-19) pandemic emerged in November 2019, various international guidelines and local protocols have been published to assist clinicians face the pandemic effectively. Medical and ventilatory strategies have evolved and researchers have come out with multiple studies and solutions within a short period of time. The patient's best interest is always the goal of the management. We present a case report of COVID-19 pneumonia in a patient with underlying Eisenmenger syndrome and the potential benefits of high-flow nasal oxygen therapy in this patient.