Purpose <p>We performed intraoperative pericardial three-dimensional echocardiography (IP3DE) for atrioventricular valve (AVV) repair in patients with congenital heart disease. In this study, we retrospectively reviewed the surgical cases of AVV repair and assessed the impact of IP3DE.</p> Methods <p>We reviewed the medical records of patients who underwent AVV repair at Nagano Children’s Hospital. Patients were divided into two groups, the IP3DE group and the control group, which underwent two-dimensional transesophageal or transthoracic echocardiography. Clinical data, including the grade of regurgitation and re-intervention, were compared between the two groups.</p> Results <p>Forty-six patients in the IP3DE group and 35 in the control group were included. The preoperative median grade was 3 (maximum 2–minimum 4) and 3 (2–4) in the IP3DE and control groups, respectively. After surgery, median grade was decreased to 1 (1–4) and 2 (1–4) in the IP3DE and control groups, respectively. 80% and 54% of patients showed successful outcome (grade ≤ 2 after repair) in the IP3DE and control groups, respectively, which demonstrated that IP3DE contributed significantly to successful outcome (<i>p</i> &lt; 0.05).</p> Conclusions <p>This study demonstrated, for the first time, the effectiveness of IP3DE in AVV repair in pediatric patients. IP3DE allows the visualization of clear 3D images and easy information sharing among cardiac vascular surgeons.</p>