Mutations in SCN5A have been reported to cause several types of hereditary arrhythmias (overlap syndrome). We herein report two patients with the overlapping phenotypes of juvenile sick sinus syndrome (SSS) and Brugada syndrome (BrS). The proband was a man who was in his twenties and had been diagnosed with both SSS and ventricular tachycardia (VT). A pilsicainide challenge test revealed a coved type ST segment elevation. His teenage brother also suffered from SSS, but no VT had been documented. A pilsicainide challenge failed to produce a Brugada-type ST elevation, but there was a marked prolongation of the His-ventricle interval. Their electrocardiograms at rest did not display any Brugada-type ST elevations. We identified a novel SCN5A (F1775Lfs*15) mutation in both patients, even though there was a phenotype discrepancy.