Background: The Nuss procedure is widely used for correcting pectus excavatum. However, the likelihood of dense substernal adhesion is high in patients with pectus excavatum after post-congenital heart disease surgery; thus, collaboration between a congenital cardiac surgeon and a thoracic surgeon is necessary for safe surgery. This study aimed to verify the feasibility of pectus surgery in children with pectus excavatum following cardiac surgery. Methods: In total, 18 patients who underwent pectus procedures for pectus excavatum from February 2011 to September 2023 and who developed after surgery for congenital heart disease were retrospectively analyzed based on their medical records. A thoracic surgeon and a congenital heart surgeon performed the surgeries. Results: The duration from cardiac surgery to Nuss surgery was 68.6 ± 38.44 months. The Nuss procedure was performed for cosmetic purposes: simultaneous Nuss surgery during conduit change, right ventricle decompression, airway decompression, and right pulmonary artery decompression in 10 (55.6%), three (16.7%), two (11.2%), two (11.2%), and one (5.6%) patient(s), respectively. The mean surgical time for Nuss bar insertion and hospitalization period was 148.6 ± 53.86 minutes and 8.4 ± 3.19 days, respectively. Twelve patients underwent Nuss bar insertion under partial sternotomy, and five patients underwent surgery using sternotomy. In one case, cardiac perforation occurred during partial sternotomy. Therefore, cardiac repair was performed using cardiopulmonary bypass after sternotomy. Conclusions: Severe adhesions between the heart and substernum from previous surgeries increase the risk of cardiac rupture during surgery; thus, collaboration with experienced congenital cardiac surgeons is essential. Careful planning and teamwork are fundamental to achieving good surgical outcomes.