Background Postoperative infection contributes to the worsening of congenital cardiac surgery (CCS) outcomes. Surgical site infection (SSI), bloodstream infection (BSI) and ventilator associated pneumonia (VAP) are common. An additional bundle of preventive measures against central-line associated bloodstream infection (CLABSI) bundle was implemented in April 2019. Objectives To compare the incidence of major infections after pediatric CCS before and after the implementation of the CLABSI bundle and to identify risk factors for major infections. Methods We conducted a single-center, retrospective study to assess the incidence of major infections including bloodstream infection (BSI), surgical site infection (SSI), and ventilator-associated pneumonia (VAP) after pediatric CCS one year before and after implementation of the CLABSI bundle during April 2018–March 2020. The demographics and outcomes of the patients were explored, and risk factors for major infections were identified using multivariate analysis. Results A total of 548 children (53% male) underwent CCS with a median age of 1.9 years (range 0.01–17.5 years). The median Aristotle Basic Complexity score was 7.1 (range 3–14.5). The CLABSI bundle was applied in 262 patients. Overall mortality was 5.5%. 126 patients (23%) experienced major postoperative infections. During the year after the implementation of the CLABSI bundle, BSI was reduced from 8.4% to 3.1% (p = 0.01), with a smaller reduction in VAP (21% to 17.6%; p = 0.33). The incidence of SSI was unchanged (1.7% to 1.9%; p = 0.77). The independent risk factors for major infections were age at surgery <6 months (p = 0.04), postoperative ventilator usage >2 days (p < 0.01), central line usage >4 days (p = 0.04), and surgery during the pre-CLABSI bundle period (p = 0.01). Conclusion Following the implementation of the CLABSI prevention package in our pediatric CCS unit, the incidence of BSI was significantly reduced. The incidence of VAP tended to decrease, while the SSI was unchanged. Sustainability of the prevention package through nurse empowerment and compliance audits is an ongoing challenge.