A 2-year-old intact female pomeranian dog presented dyspnea, labored breathing, cough, exercise intolerance, machinery heart murmur, and precordial thrill. A left-to-right patent ductus arteriosus (PDA) was diagnosed based on two-dimensional echocardiography, thoracic radiography, electrocardiography, and blood work. An angiography was performed to accurately evaluate the size and shape of the duct. An interventional approach for transcatheterial occlusion of the PDA was achieved using an Amplatz® Canine Duct Occluder (ACDO), which is a commercially available ductal occluding device. Due to the limited size of the dog’s femoral artery, a device smaller [125% of minimal ductal diameter (MDD); recommended size: 150~200% of MDD] than recommended was mounted. After placement of the ACDO, precordial thrill and continuous heart murmur disappeared, and the patient was discharged the next day after stabilization with O2 supply. Upon follow up examination, dyspnea, labored breathing, cough, exercise intolerance, and cardiomegaly were improved with no complications after the procedure. The ACDO was well maintained in position. This case represents successful clinical application of the Amplatz® Canine Duct Occluder to achieve closure of a PDA using a slightly smaller device than the recommended size.