Introduction: Total abnormal pulmonary venous return anomaly (TAPVD) is a congenital heart disease characterized by abnormal pulmonary venous drainage to the right atrium. The Neutrophil/Lymphocyte Ratio (NLR) is used to predict mortality and morbidity after congenital heart surgery. In this study, the effect of postoperative NLR changes on prolonged intensive care unit stay in newborns with TAPVD was searched. Patients and Methods: The newborns with TAPVD who were followed up and operated on in the pediatric cardiac intensive care unit between May 1, 2020, and May 1, 2022, were included in the study. Hematological parameters and NLR changes were recorded before and after the operation (1st-2nd-3rd days). Long ICU duration (PCILOS, being in the longest 25 percent as duration) was accepted as morbidity. The effects of NLO changes on PCILOS were examined. Results: Twenty-four patients were included in the study. The median age was 18 days (IQR 12 days-24 days) and the median weight was 3 kg (IQR= 2.8-3.2). Fifteen patients were male (63%). Median mechanical ventilator duration, intensive care unit stay, and hospital stay were 40 hours (IQR= 30-48 hours), seven days (IQR= 5-9), and 15 days (IQR= 12-18), respectively. PCILOS duration was determined as >9 days. Three patients (12.5%) died in the postoperative first 30 days. Preoperative NLR value> 1.9 and postoperative 3rd day NLR> 2.8 predicted PCILOS strongly. Conclusion: High NLR values in the preoperative and early postoperative periods of neonates with total abnormal pulmonary venous return anomaly may be helpful to predict prolonged ICU stay.