We investigated whether liver stiffness (LS) quantified using magnetic resonance elastography (MRE) could predict the prognosis of advanced hepatocellular carcinoma (HCC) patients treated with sorafenib. We selected 50 sorafenib-treated advanced HCC patients who underwent MRE within 3 months before drug administration from a prospectively maintained cohort of chronic liver disease patients, according to the inclusion and exclusion criteria. Univariate and multivariate analyses were performed to evaluate the prognostic role of laboratory data, tumor characteristics, and MRE-assessed LS for overall survival (OS), progression-free survival (PFS), and significant liver injury (grade ≥ 3) after sorafenib administration. High MRE-assessed LS either as continuous (per kPa, hazard ratio (HR) 1.54; 95% confidence interval (CI) 1.23-1.92, p < 0.001) or categorical (> 7.5 kPa, HR 4.06, 95% CI 1.40-11.79, p < 0.01) variable was significantly associated with poor OS along with higher serum alpha-fetoprotein (AFP, ≥ 400 ng/mL) and advanced tumor stage (modified Union for International Cancer Control (mUICC) IVb). Higher MRE-assessed LS was also significantly associated with the development of significant liver injury after sorafenib administration (per kPa, HR 1.62, 95% CI 1.21-2.17, p = 0.001; > 7.5 kPa, HR 10.11, 95% CI 2.41-42.46, p = 0.002). PFS analysis identified higher serum AFP (≥ 400 ng/mL) and advanced tumor stage (mUICC IVb) as significant risk factors for early disease progression, whereas LS was not associated with PFS CONCLUSION: Higher MRE-assessed LS is a potential biomarker for predicting poor OS and significant liver injury in advanced HCC patients treated with sorafenib. • Higher pretreatment LS by MRE (> 7.5 kPa), higher AFP (≥ 400 ng/mL), and advanced tumor stage (mUICC IVb) were associated with poor OS in advanced HCC patients treated with sorafenib. • Higher pretreatment LS by MRE was associated with developing significant (grade ≥ 3) liver injury during sorafenib treatment, which required termination of the therapy. • Patients with high pretreatment LS by MRE should be monitored carefully for potential liver injury during sorafenib treatment.