Coronary artery fistulae (CAF) are rare congenital anomalies and reported to have an incidence of 0.1–0.2% of all coronary angiograms. An association between fistulae and nonatherosclerotic coronary artery aneurysms is even more rare. In childhood, patients are mostly asymptomatic; however, patients older than 20 years old may present with signs of infective endocarditis, myocardial ischemia, congestive heart failure, and aneurysm rupture. CAF are typically identified by coronary angiography; however, there are some limited studies showing that transesophageal echocardiography (TEE) can also be useful in identifying CAF. Here we report two cases of endocarditis secondary to congenital coronary artery fistulae draining into either a cardiac cavity or a coronary sinus, which were detected by TEE. Vegetations were found at the site of the fistulae drainage. Management for young patients is either percutaneous or surgical intervention. For elderly patients with multiple comorbidities, conservative treatment is another option. In these two cases, treating endocarditis with proper antibiotics and supportive treatment, the patients' conditions improved significantly.