AIM: Pectus excavatum (PE) is a common congenital chest wall deformity that can impair cardiopulmonary function. While minimally invasive Nuss surgery is widely recognized for its cosmetic benefits, its early effects on cardiopulmonary performance are still unclear. This study aimed to investigate the changes in restrictive breathing patterns and cardiac parameters in the early postoperative period. METHODS: A retrospective analysis was performed on 97 patients (26 females, 71 males) treated for pectus excavatum with a Haller index (HI) ≥3.25 at the Department of Thoracic Surgery between October 2008 and July 2020. Spirometric measurements were performed to assess lung function, including forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Cardiac parameters such as left ventricular ejection fraction (EF) and right ventricular diameter (RVD) were determined using transthoracic echocardiography. The examinations were performed preoperatively and six months postoperatively. RESULTS: Significant improvements were observed in FVC (68.3% to 75.4%, p = 0.01) and EF (55.2% to 62.8%, p = 0.02) after the Nuss surgery, while the changes in FEV1 (p = 0.07) and RVD (p = 0.09) were not statistically significant. A subgroup analysis by HI severity showed that patients with moderate HI (3.25–4.0) had significantly higher preoperative (p = 0.0001) and postoperative (p = 0.0007) FVC, as well as preoperative (p = 0.004) and postoperative (p = 0.002) EF compared to those with severe HI (>4.0). Differences in ∆FVC (p = 0.15) and ∆EF (p = 0.20) between the groups were not statistically significant. Notably, FEV1 showed greater improvement in the moderate group (p = 0.035). An age-based analysis showed that patients under 18 years had significantly higher preoperative (p = 0.003) and postoperative (p = 0.002) FVC and postoperative EF (p = 0.008), though ∆FVC (p = 0.33) and ∆EF (p = 0.25) did not differ between age groups. Although FEV1 increased more in younger patients, this difference was not significant (p = 0.06). Gender-based analysis demonstrated that female patients had significantly higher preoperative (p = 0.02) and postoperative (p = 0.05) FVC, as well as postoperative EF (p = 0.03), compared to male patients. Although some parameters did not reach significance, the trends suggest potential long-term cardiopulmonary benefits. CONCLUSIONS: Nuss surgery leads to a significant improvement in FVC and EF, especially in younger patients and those with moderate HI deformities. Although some changes were not statistically significant, the overall trends suggest potential long-term cardiopulmonary benefits. Further studies are needed to confirm these results and evaluate long-term outcomes.