The study aimed to evaluate the effect of the SYNTAX score (SS) calculated before percutaneous intervention on survival in a group of young patients with acute coronary syndrome (ACS). Our study is a retrospective study. Patients between the ages of 18 and 45 who applied to Private Yalova Atakent Hospital Cardiology Clinic with ACS and underwent percutaneous coronary intervention between 01.01.2017 and 01.12.2023 were included in the study. Patients aged 45 and under who presented with acute syndrome and underwent coronary angiography were evaluated. Patients' history of major cardiac adverse events (MACE) was evaluated. Demographic characteristics, laboratory findings, echocardiographic parameters, and SS of the patients were recorded. SS was calculated from the coronary angiography images of the patients. 140 patients were included in the study. 70.0% (n=98) of the cases were diagnosed with ST-elevation myocardial infarction (STE-MI), 28.6% (n=40) with non-ST-elevation myocardial infarction (NSTE-MI)-unstable angina pectoris (USAP), and 1.4% with cardiac arrest (n=2). 28.6% (n=40) of the patients had MACE. There was a statistically significant correlation between SS and MACE (r=0.525 p=0.001). An SS value of 23.15 had 77.5% sensitivity and 60.8% specificity in predicting MACE. There was a statistically significant negative correlation between SS and ejection fraction (EF) (r=-0.584, p=0.001). EF<40.5 predicted mortality with 77.7% sensitivity and 69.4% specificity (AUC 0.710, p=0.01, 95% CI 0.615-0.825). SYNTAX Score and EF have predictive value in predicting MACE and mortality in young ACS patients. Different scoring systems are needed to predict MACE and mortality after ACS in young patients.