BACKGROUND: Previous meta-analyses have investigated the efficacy of lipid-lowering therapies for atherosclerotic cardiovascular disease; however, few have focused on patients with acute coronary syndrome (ACS). This meta-analysis aimed to compare the benefits of intensive lipid-lowering therapy with those of background statin therapy in patients with ACS. METHODS: Searches were performed on PubMed, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov databases for articles published until April 13, 2023. Randomized controlled trials that compared intensive lipid-lowering therapies and background statin therapies in patients with prior ACS and recorded the outcome of three-point major cardiovascular events (MACE) were included. The risk ratio (RR) with 95% confidence interval (CI) was used as a measure of primary and secondary outcomes. RESULTS: Nine trials involving 38,640 patients with ACS were identified. Pooled results suggested that intensive lipid-lowering therapies are associated with a reduction in the risk of three-point MACE (RR, 0.88; 95% CI, 0.83-0.94;  < 0.001), recurrent ACS (RR, 0.82; 95% CI, 0.71-0.96;  = 0.013), nonfatal myocardial infarction (MI) (RR, 0.87; 95% CI, 0.81-0.93;  < 0.001), stroke (RR, 0.83; 95% CI, 0.73-0.94;  = 0.003), and unstable angina-related hospitalization (RR, 0.57; 95% CI, 0.33-0.99;  = 0.046), but not all-cause mortality (RR, 0.94; 95% CI, 0.82-1.07;  = 0.329), cardiovascular disease-related mortality (RR, 0.96; 95% CI, 0.88-1.06;  = 0.457) or coronary revascularization (RR, 0.89; 95% CI, 0.79-1.00;  = 0.057). CONCLUSIONS: Intensive lipid-lowering therapies may reduce the risk of three-point MACE, recurrent ACS, nonfatal MI, stroke, and hospitalization for unstable angina in patients with ACS undergoing background statin therapy. These results may assist in clinical decision-making for the secondary prevention of cardiovascular events to initiate intensive lipid-lowering therapies immediately after ACS.