The aim of the study is to investigate the impact of two different cardioplegia solutions, the del Nido (dN) and blood cardioplegia (BC), on postoperative troponin concentrations, vasoactive-inotrope score, and length of hospital stay in pediatric patients undergoing cardiovascular surgery for CHD. 80 subjects aged between 1 and 120 months who were scheduled for surgical repair for a CHD were prospectively enrolled in this study. Study subjects were allocated to one of the study groups using simple randomization technique as follows: The del Nido cardioplegia group (n = 40, median age 8.5 [5.5–14] months) and conventional blood cardioplegia group (n = 40, median age 11 [5–36] months). Aortic cross-clamp time and cardiopulmonary bypass time were recorded in all subjects. Troponin I and vasoactive-inotropic score, which indicates the amount of cardiovascular support by various inotropes or vasopressors, were recorded following the repair. The difference in troponin I, vasoactive-inotropic score (VIS), length of ICU stay, and length of hospital stay between the two groups was the primary outcome measure of this study. The volume of cardioplegia was significantly lower in dN group than that of the BC group (p < 0.001). Cardiopulmonary bypass time and aortic cross-clamp time were significantly shorter in subjects receiving dN cardioplegia than those receiving BC (p = 0.006, and p = 0.001, respectively). Subjects assigned to BC had higher Troponin I concentrations at postoperative 24th hour compared to subjects receiving dN cardioplegia [1.60 (0.92–2.49) ng/mL vs. 1.03 (0.55–1.83) ng/mL, p = 0.045]. VIS was also significantly higher in BC group at 24th [10 (10–13) vs. 10 (5–10), p = 0.032] and 48th hours [10 (1.5–10) vs. 0 (0–10), p = 0.005] compared to that of the dN cardioplegia group. The median extubation time was 7.5 (3.5–20.5) hours in dN cardioplegia group and 5 (4–10) hours in the BC group (p = 0.384). There were no significant differences between the groups with respect to the length of ICU stay and length of hospital stay. No mortality and no significant arrhythmias requiring medical or electrical cardioversion were noted in any of the groups. In conclusion, dN cardioplegia provides shorter aortic cross-clamp time and cardiopulmonary bypass time, and lower postoperative troponin I concentration and vasoactive-inotrope scores compared to BC in pediatric subjects undergoing surgical repair for CHD. However, lengths of ICU and hospital stay are similar in dN cardioplegia and BC groups.