Background: Over recent years, our institution has progressively refined its surgical strategy for ostium secundum atrial septal defect (ASD II) closure. The approach evolved from conventional total sternotomy to mini-sternotomy and, most recently , to right-sided mini-thoracotomy . Objective: To evaluate the safety and efficacy of these evolving techniques for ASD II closure, highlighting the transition toward minimally invasive surgery . Methods: We conducted a retrospective analysis of 100 consecutive pediatric patients who underwent surgical ASD II closure between January 2017 and December 2024 at the University Children’s Hospital of Cracow . Surgical access was categorized as total sternotomy (TS, 39%), mini-sternotomy (MS, 55%), and right-sided mini-thoracotomy (RSMT, 6%). Results: The cohort consisted predominantly of females (66.3%). Median age at surgery was 3.5 years (IQR 1.5–6.5), with a median weight of 20.7 kg. Mean cardiopulmonary bypass time was 50.4 minutes for RSMT and 38.4 minutes for MS, remaining comparable to TS. Primary closure was achieved in 77% of patients, while the remainder required an autologous pericardial patch. Median hospital stay was similar across groups (IQR 3–7 days). Postoperative complications were rare; one patient required reoperation for residual shunt. No neurological events were observed, and there was no 30-day mortality . Conclusions: Minimally invasive ASD II closure is a safe and effective alternative to conventional sternotomy . Right-sided mini-thoracotomy , although technically demanding, offers excellent cosmetic outcomes and represents a promising direction for further development in pediatric congenital cardiac surgery .