Background: Nonalcoholic fatty liver disease (NAFLD) is regarded as a component of metabolic syndrome, which has insulin resistance (IR) as the primary physiopathological event. The aim of study was to establish the association between IR, assessed using triglyceride and glucose index (TyG), and histopathological features of NAFLD lesions. Methods: The study included patients with metabolic syndrome. Fasting plasma glucose (FPG), fasting lipid profiles and liver enzymes were measured. IR was assessed by TyG index. Liver biopsy was performed for assessment steatosis and fibrosis. Results: TyG index had a mean value of 8.93 ± 1.45, with a higher value in the patients with overweight (p=0.002) and obesity (p=0.004) than in the patients with normal weight. TyG index mean value of 8.78 ± 0.65 in subjects without NASH, 8.91 ± 0.57 in patients with borderline NASH and 9.13 ± 0.55 in patients with definite NASH. Significant difference was found between subjects without NASH and the ones with definite NASH (p=0.004). The analysis of the area under the ROC curve proved that TyG index is a predictor for NASH (p=0.043). Conclusion: TyG index is a facile tool used to identify individuals at risk for NAFLD, but not for the progression of liver lesions.