Background: Congenital heart disease (CHD) is a leading cause of childhood morbidity, with an estimated prevalence of 0.8–1%. However, advances in diagnosis and treatment now allow 90% of childhood CHD patients to survive to adulthood, leading to increased interest in their quality of life (QoL). In this study, we examine the impact of clinical and psychosocial variables, including the number of surgical interventions (NSI), age at surgery, school achievement, and social support, as mediating factors of QoL in CHD patients. Methods: The study included 233 CHD patients (132 males) with an average age of 15.2 \pm 2.07 years, including 80 with cyanotic CHD and 153 with acyanotic CHD. The severity of illness ranged from mild to severe, with 30 patients having a severe illness, 119 having a moderate illness, and 84 having a mild illness. One-hundred-sixty-three patients underwent surgery. Clinical data on diagnosis, the severity of CHD, the type of CHD, and surgical interventions were collected from patient records, and a semi-structured interview was conducted to explore the relationship between CHD diagnosis and various aspects of life. QoL was assessed using the Abbreviated World Health Organization Quality of Life questionnaire (WHOQOL-Bref) questionnaire. Results: Ten mediation models were analyzed, each with three hypotheses (paths). In all models the first hypothesis was supported. Analyses of the second and third hypotheses revealed three feasible models of mediation through the effect of NSI on QoL in CHD patients. Conclusions: Our findings indicate that patients with more severe and cyanotic CHD generally require more surgical interventions, which may increase the risk of negative outcomes and affect patients’ perception of QoL. These results have important implications for healthcare providers and psychologists who work with childhood CHD patients.