Propionic acidemia and long QT syndrome (LQTS) are rare disorders. In addition, both conditions are potentially lethal. The patient presented in this article was initially diagnosed with propionic acidemia. Incidentally, she was found to have LQTS on electrocardiogram and verified by stress test and epinephrine challenge. Although the patient was asymptomatic and arrhythmia free, we started her on atenolol. This is the first report of the association between LQTS and propionic acidemia.