The variations on the venous system’s conformation are closely related with the embryological development, due to atrophy or persistency of embryological connections that this system establishes for its final formation. During a routine dissection of a heart-lung block of a male Caucasian cadaver (40 % formolized), at the Dissection Team of the Second Chair of Anatomy, School of Medicine, University of Buenos Aires, our team found a persistent left superior vena cava (PLSVC), with its right superior vena cava (RSVC) missing. In addition, the PLSVC was draining to a dilated coronary sinus. Before the PLSVC drains, it receives the corresponding Acygos vein, which describes its journey above the left pulmonary root. It is essential for the specialist physician to be aware of the existence of this variation in order to address and resolve safely the procedure and the existing pathology of the patient, since, most of the time, this vascular anomaly is found incidentally in the context of a CT, echocardiogram, or during the placement of endocavitary catheters.