Background: Pressure injury (PI) is a prevalent complication in pediatric cardiac surgery, with higher incidence than in general pediatric populations due to children’s thin skin, underdeveloped subcutaneous tissue, and prolonged intraoperative pressure. Objective: To evaluate the effectiveness of the curvilinear supine position (CSP) in preventing PI among children undergoing congenital heart disease (CHD) surgery. Methods: Between October 2024 and February 2025, a single-center randomized controlled trial was conducted. Of the 80 children initially enrolled for congenital heart disease (CHD) surgery, 77 (aged 1 month to 14 years) completed the study and were included in the final analysis after 3 were excluded due to protocol violations. Participants were randomly assigned to the CSP group (n = 38) or the conventional supine position group (n = 39). Results: The incidence of PI was significantly lower in the CSP group (2.6%) compared to the control group (20.5%) (p = 0.029). Postoperative LDH levels were also significantly reduced in the CSP group (422.67 ± 86.52 U/L vs. 592.92 ± 215.71 U/L; p = 0.031), while preoperative LDH and surgical variables (e.g., cardiopulmonary bypass time) were comparable between groups. Although the CSP group had a shorter hospital stay (17.24 vs. 22.51 days), the difference was not statistically significant (p = 0.085). Caregiver satisfaction was significantly higher in the CSP group (100.0% vs. 84.6%; p = 0.025). Conclusion: CSP effectively reduces PI incidence, mitigates tissue injury, and enhances caregiver satisfaction in pediatric cardiac surgery, offering a safe and feasible strategy for perioperative PI prevention.