Background. Transposition of the great arteries (TGA) is a complex congenital heart disease that requires early diagnosis as well as advanced surgical repair and postoperative support. This study sought to investigate the impact of surgical timing on early postoperative morbidity.Methods. This study reviewed all patients with TGA repaired at a single institution (Skåne University Hospital, Lund, Sweden) by arterial switch operation (ASO) between June 2001 and June 2017. Major postoperative morbidity (MPM) and death within 30 days after ASOs were documented. Patients with double-outlet right ventricle, chromosomal abnormalities, and noncardiac diseases were excluded. MPM was defined as the presence of at least 1 of the following: delayed sternum closure, reoperation, prolonged mechanical ventilation, noninvasive ventilation after extubation, peritoneal dialysis, extracorporeal membrane oxygenation, and readmission.Results. A total of 241 patients were included, with medians for birth weight, gestational week, and age at surgery of 3.5 kg, 39 weeks, and 5 days, respectively. MPM was encountered in 32.3% of patients. Prematurity (P [ .001) and need for aortic arch repair at the time of ASO (P [ .04) were associated with a significant increase in MPM. Non-A coronary anatomy, associated ventricular septal defect requiring surgical closure, and fetal diagnosis of TGA had no significant impact on MPM (P [ .35, .08, and .21, respectively). There was no significant difference in MPM among the surgical groups (P [ .49).Conclusions. Early complications after ASO do occur and are mostly associated with prematurity and the need for aortic arch repair. Timing of surgical repair does not seem to influence the rate of these complications.