ObjectiveTo systematically evaluate the prognostic value of the triglyceride-glucose (TyG) index in predicting cardiovascular outcomes in patients with acute coronary syndrome (ACS). MethodsThe PubMed, Embase, Cochrane Library, Web of Knowledge, CBM, WanFang Data and CNKI databases were electronically searched to collect cohort studies investigating the association between the TyG index and ACS prognosis from inception to January 25, 2025. Two reviewers independently screened literature, extracted data and assessed the risk of bias of the included studies. Meta-analysis was then performed by using RevMan 5.4 and Stata 18.0 software. ResultsA total of 18 studies involving 30 769 patients were included. The meta-analysis revealed that the TyG index was associated with ACS prognosis. When the TyG index was treated as a categorical variable, higher TyG index was significantly associated with an increased risk of MACE compared to lower TyG index (HR=1.94, 95%CI 1.62 to 2.31, P<0.001). Subgroup analysis indicated that the association between the TyG index and MACE remained independent of gender, age, participant characteristics, hypertension, and diabetes. In patients with ACS but without chronic kidney disease, the TyG index demonstrated a strong correlation with MACE (P=0.006). However, in ACS patients with concurrent chronic kidney disease, the TyG index did not appear to be a suitable predictor of MACE (P=0.22). ConclusionThe TyG index demonstrates a strong correlation with MACE in ACS patients, where a higher TyG index is associated with an increased incidence of MACE, indicating poorer prognosis. The TyG index may serve as a simple surrogate marker for prognostic prediction in ACS patients, independent of sex, age, participant characteristics, hypertension, and diabetes. However, its application is currently limited in ACS patients with comorbid CKD.