Objective: to evaluate the impact of lipoprotein (a) [Lp(a)] levels on long-term outcomes in patients with acute coronary syndrome (ACS) and single-vessel coronary artery disease. Materials and methods: the study included 110 patients diagnosed with ACS and single-vessel coronary artery disease. Patients were divided into two groups based on Lp(a) levels: Lp(a) > 50 mg/dL (n=22) and Lp(a) < 50 mg/dL (n=88). Primary outcomes included survival and the frequency of recurrent cardiovascular events at 6, 12, and 36 months. Statistical analysis included t-test, chi-square test, Kaplan-Meier method, and Cox multivariate regression. Results: at 36 months, patients with high Lp(a) levels had significantly higher rates of recurrent myocardial infarctions (50% vs. 34.1%, p < 0.001) and all-cause mortality (59.1% vs. 23.9%, p < 0.001) compared to patients with normal Lp(a) levels. Conclusion: high Lp(a) levels are a significant prognostic factor for worse long-term outcomes in patients with ACS and single-vessel coronary artery disease. Measuring Lp(a) levels may improve management strategies for these patients.