Cor triatriatum dexter (CTD) is an extremely rare pathology, with an incidence of < 0.4%. Its main characteristic is a partitioning of the right atrium by the persistence of the embryonic valve of the right sinus venosus.In this report, we describe the case of a 7-day-old newborn who presented with persistent cyanosis associated with feeding and crying. The diagnosis of CTD was made after an echocardiogram and confirmed using cardiac magnetic resonance imaging. The patient underwent successful surgery on day 14 with a favorable outcome and without complications.The importance of our case lies in the identification of rare heart disease as a cause of cyanosis and desaturation in a neonatal patient in the first days of life who did not present signs of heart failure and whose condition improved with supplemental oxygen. We also demonstrate that early diagnosis with echocardiography and surgical resolution resulted in clear clinical improvement and avoided future complications.