OBJECTIVE To systematically review the efficacy and safety of ticagrelor versus clopidogrel in CYP2C19 loss-of-function carriers with mild ischemic stroke or transient ischemic attack(TIA). METHODS Databases such as PubMed, Embase, the Cochrane Library, CNKI, and Wanfang were systematically searched, and the search period was from database establishment to June 2022. Two reviewers independently screened literature, extracted data, and evaluated the methodological quality of the included studies. Meta-analysis was performed using RevMan 5.3 software. RESULTS A total of 2 studies with 7 087 patients were included. Compared with clopidogrel, ticagrelor reduced the incidence of stroke[RR=0.78, 95%CI(0.66−0.93), I2=0%, P=0.007] and vascular event[RR=0.78, 95%CI(0.66−0.91), I2=0%, P=0.002] in patients with mild ischemic stroke or TIA carrying the CYP2C19 loss-of-function allele. The incidence of any bleeding[HR=2.18, 95%CI(1.66−2.85)] and minor bleeding[HR=2.41, 95%CI (1.81−3.20)] in the ticagrelor-aspirin group was higher than that in the clopidogrel-aspirin group, and dyspnea (1.2% vs 0.2%, P<0.001) and arrhythmias(1.7% vs 0.8%, P=0.001) were more common in the ticagrelor-aspirin group than in the clopidogrel-aspirin group. There was no significant difference in the incidence of severe bleeding between the two groups. CONCLUSION Compared with clopidogrel, ticagrelor reduces the incidence of stroke and vascular events in patients with mild ischemic stroke or TIA carrying the CYP2C19 loss-of-function allele, and did not increase the risk of severe bleeding. However, the ticagrelor group had a higher incidence of minor bleeding, dyspnea and arrhythmias.