Aim We aimed to analyze the dispersion slope (DS) using shear wave dispersion (SWD) in patients with Fontan-associated liver disease (FALD) and to investigate its utility as a biomarker of disease progression. Methods This cross-sectional study enrolled 27 adults with FALD who underwent SWD, two-dimensional shear wave elastography (2D-SWE), transthoracic echocardiography, cardiac catheterization, or abdominal computed tomography (CT) from April 2019 to April 2021. According to CT findings, patients were divided into two groups: significant fibrosis and non-significant fibrosis. Results The median DS in the control (n = 10), non-significant fibrosis (n = 12), and significant fibrosis (n = 15) was 9.35, 12.55, and 17.64 (m/s)/kHz, respectively. The significant fibrosis group showed a significantly higher DS than non-significant fibrosis group (P = 0.003). DS showed a significant correlation with central venous pressure (r = 0.532, P = 0.017) and liver stiffness measurements using 2D-SWE (r = 0.581, P = 0.002). The areas under the receiver operating characteristic curve for the diagnosis of significant fibrosis were 0.903 and 0.734 for SWD and 2D-SWE, respectively (P = 0.043). Conclusions DS measured by SWD reflects the severity of liver damage in patients with FALD. SWE may be valuable for the therapeutic management of patients with FALD.