In this study we describe the echocardiographic features of a complex cardiac defect with a right to left shunt through tetralogy of Fallot and also a left to right shunt through a patent ductus arteriosus (PDA) in a 3-year-old dog. The echocardiography revealed a tetralogy of Fallot with a severely hypertrophied right ventricular outflow tract (RVOT), and a left to right shunting PDA. A contrast echocardiogram showed microbubbles moving from the right ventricle to the aorta through the ventricular septal defect. They then reached the main pulmonary artery through the PDA rather than through the RVOT. The necropsy confirmed tetralogy of Fallot with an RVOT obstruction and a PDA. This patient could have maintained the pulmonary circulation through the PDA in the spite of the right ventricular outflow tract obstruction and survive a long period. Not only the echocardiography, but also the contrast echocardiogram using agitated saline and trans-sectional images in CT enhanced the comprehensive understanding of the anatomic defects in this complex cardiac defect.