The efficacy of minimally invasive cardiac surgery (MICS) has often been reported. However, in Japan most of these procedures are supported with robotic systems, which are expensive. We report the technique of atrial septum defect (ASD) closure by MICS and a three-dimensional endoscope without the aid of a robotic system. From March 2012 to April 2015, we performed ASD closure using this method in 7 patients. The use of a three-dimensional endoscope enables cardiac surgery to be performed through smaller incisions (≤5 cm in width). We have adopted this method of ASD closure with the Maze procedure for patients complicated by atrial fibrillation. The operation time will decrease as we improve our surgical technique. Our current practice is to attempt ASD closure with totally endoscopic support.