Aim Triglyceride glucose index (TyG index) is a surrogate marker for insulin resistance. No studies have evaluated the TyG index in patients with coronary slow flow phenomenon (CSFP). We investigated TyG index values in CSFP and evaluated whether it had a predictive value for the diagnosis of CSFP.Material and Methods 132 CSFP patients and 148 subjects with normal coronary arteries were included in the study. Thrombo-lysis in myocardial infarction frame count (TFC) of each patient was calculated. Demographic, clinical features, information regarding medication use and biochemical variables of the patients were obtained from hospital records.Results TyG index of patients with CSFP and normal coronary flow were 9.02 (8.65-9.42) and 8.69 (8.39-9.18), respectively (p<0.001). Mean TFC showed positive correlation with the TyG index, glucose, triglyceride, and hemoglobin concentration (r=0.207, r=0.138, r=0.183, r=0.179 and p<0.001, p=0.020, p=0.002, p=0.003, respectively) and negative correlation with high density lipoprotein-cholesterol (HDL-C) level (r=-0.292, p<0.001). Receiver operating characteristic curve analysis of TyG index demonstrated that the value of 8.68 predicted CSFP curve analysis of TyG index demonstrated that the value of 8.68 predicted CSFP with sensitivity of 74.2 % and specificity of 58.6 %. In multivariate logistic regression analysis, HDL-C, hemoglobin and the TyG index were the independent predictors of CSFP.Conclusions Our findings supported the hypothesis that insulin resistance play role in CSFP.