Recent studies have shown similar safety and efficacy of short-term dual antiplatelet therapy (DAPT) followed by P2Y12 inhibitor (P2Y12i) monotherapy when compared with standard DAPT. However, the optimal DAPT duration and regimen in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) is still unclear. Online databases were searched for randomized controlled trials (RCTs) evaluating P2Y12i monotherapy after short DAPT (≤3 months) vs standard DAPT (≥12 months) in ACS patients. The outcomes of interest were all cause death, cardiovascular (CV) death, myocardial infarction (MI), stent thrombosis (ST), target-vessel revascularization (TVR) and major bleeding. Random-effects model was used to calculate pooled odds ratios (OR) and 95% confidence intervals (CI). Six RCTs with a total of 23,884 patients (n=11,904 P2Y12i monotherapy, n=11,980 standard DAPT) were included. Compared with standard DAPT, P2Y12i monotherapy after short DAPT was associated with similar odds of all cause death (OR 0.86, 0.65-1.12, p = 0.26) and CV death (OR 0.75, 0.43-1.29, p = 0.29) at 1 year. Similarly, there were no significant differences in rates of MI (OR 1.09, 0.83-1.43, p = 0.53), ST (OR 1.09, 0.71-1.67, p = 0.70) and TVR (OR 0.81, 0.65-1.01, p = 0.07) between the P2Y12i monotherapy and standard DAPT arms. The P2Y12i monotherapy group had significantly lower major bleeding (OR 0.49, 0.38-0.64, p<0.001) when compared to standard DAPT. In conclusion, among patients with ACS undergoing PCI, P2Y12i monotherapy after short DAPT significantly reduces bleeding without increasing ischemic risk when compared to standard DAPT therapy.