This case report is the first detailed description of the echocardiographic findings in tetralogy of Fallot (TOF) in a newborn foal. In addition to the characteristic elements of TOF, asynchronous wall movement patterns were also evident. Measurements in 2D and M-mode echocardiography revealed marked changes in cardiac dimensions. Haemodynamic studies in both right and left ventricular outflow tracts, as well as haemodynamic studies of the shunt flow situation, were performed. Shunting flows through the ventricular septal defect in both directions, and also from the right ventricle into the aorta, were present. A mild to moderate stenosis of the pulmonary valve, as the determining factor in longterm prognosis, could be found by echocardiography.