Background and aims: Insulin resistance plays an important role in MASLD development and progression, but its accurate measurement in patients with type 2 diabetes (T2D) is problematic. Here, we evaluate the association between a recently introduced index of insulin resistance and liver steatosis and fibrosis in patients with T2D. Methods: This is a cross-sectional study based on data obtained during the 2017-2020 cycle of the National Health and Nutrition Examination Survey. Patients with T2D without chronic viral hepatitis or significant alcohol consumption were included. The insulin sensitivity (IS) index was calculated with a formula based on body mass index, urine albumin to creatinine ratio, triglycerides and gamma-glutamyl transferase. Transient elastography was performed in all patients. MASLD was defined as a controlled attenuation parameter ≥274 dB/m and significant liver fibrosis as a liver stiffness measurement ≥8 kPa. The association between estimated IS and both liver outcomes was evaluated with multivariable logistic regression models after adjustment for potential confounders. Results: A total of 1084 patients with T2D were included. Prevalence of MASLD and significant liver fibrosis were 74.1% (95%CI 68.7-78.9) and 25.4% (95%CI 21.2-30.2), respectively. In a multivariable logistic regression model adjusted for age, sex, waist circumference and race-ethnicity, a lower IS score (i.e. higher insulin resistance) was independently associated with a higher prevalence of both MASLD (quartile 1 vs quartile 4: OR 2.66, 95%CI 1.23-5.71) and significant liver fibrosis (quartile 1 vs quartile 4: OR 3.30 95%CI 1.45-7.51). Results were consistent when analyses were stratified according to age, sex and obesity. Discussion: A recent model of IS based on readily available clinical and biochemical variables is independently associated with liver endpoints. Its use might help identify patients with more advanced forms of MASLD.