Objectives of the study Nonalcoholic fatty liver disease (NAFLD) is a common condition with a subset of individuals developing liver fibrosis as a major risk factor for advanced liver disease. The contribution of genetic factors to this progression remains incompletely understood. Our aim was to analyze heritability in the development of liver fibrosis estimated by ultrasound shear wave elastography (SWE) in an asymptomatic adult twin cohort. Methods In total 172 adult Hungarian twins (51 monozygotic and 36 dizygotic pairs; 63% women; mean age 54.9 ± 15.1 years) underwent B-mode ultrasonography to assess steatosis and SWE to determine Young’s modulus as a noninvasive marker or liver fibrosis. Results We identified 99 subjects with steatosis, which was mild in 46 subjects (46%), moderate in 52 subjects (52%) and severe in a single subject (1%). Mean Young’s modulus was 7.58 ± 3.53 kPa in this slightly overweight study cohort (BMI: 25.7 ± 4.6 kg/m2). Univariate analysis adjusted for age, sex and BMI indicated no discernible role for genetic components in the presence of liver stiffness, whereas shared and unshared environmental effects accounted for 38.3% (95% confidence interval (CI), 17–56.1%) and 61.7% (95% CI, 43.9–83%). Conclusions Our findings do not support the heritability of liver stiffness in an asymptomatic, twin cohort with slight overweight and variable degree of steatosis, underscoring the importance of environmental factors in the development of NAFLD and liver fibrosis.