Background: Conventional cardiac surgery involving cardiac arrest and cardiopulmonary bypass (CPB) is well known to be associated with postoperative myocardial dysfunction and low cardiac output syndrome (LCOS). The aim of this study is to compare the effect of prophylactically administered levosimendan and milrinone on postoperative parameters and outcomes in neonates and infants after corrective open-heart surgery and comparing postoperative parameters like heart rate, mean arterial pressure, arterial and venous blood gasses at certain particular points of time. Method: We performed a prospective observational study at our institute. Total 100 pediatric patients undergoing complex congenital cardiac surgeries to evaluate the efficacy of milrinone and levosimendan on intraoperative and postoperative outcomes. Result: In the postoperative period heart rate and mean arterial pressure at three different time periods (T1, T2 and T3) did not show any statistically significant difference in both the groups. The VIS score after 48 hours was less in Group L (p = 0.0005). Serum creatinine estimated at T2 and T3 showed a statistically significant difference. (p value at T2 = <0.001, p value at T3 = 0.002). Duration of ventilation was less in Group L (p = 0.0297). Conclusion: In our prospective observational study of 100 infants undergoing surgery for complex congenital cardiac conditions, postoperative hemodynamic parameters and markers of tissue perfusion overtime were similar in infants with administration of either levosimendan or milrinone. Our results might be the basis of future controlled trials of levosimendan in children with a special focus on duration of mechanical ventilation and the incidence of renal complications.