SummaryBackgroundFibroscan‐derived liver stiffness decreases after anti‐viral treatment for hepatitis C virus (HCV) infection, which may affect the associations and interpretation of liver stiffness.AimsTo assess whether liver stiffness pre‐ or post‐anti‐viral therapy is associated with the development of decompensated cirrhosis, hepatocellular carcinoma (HCC) or death.MethodsIn this retrospective cohort study, we identified US veterans who initiated HCV treatment and had at least one liver stiffness before (n = 492) or after (n = 877) HCV therapy. We used Cox proportional hazards regression (adjusting for age, race/ethnicity, history of cirrhosis, body mass index, diabetes, FIB‐4 score, Charlson comorbidity index, alcohol use disorder, Model for end‐stage liver disease score and sustained virological response status) to determine the associations between pre‐ or post‐treatment liver stiffness values and the development of decompensated cirrhosis, HCC, death or liver transplant.ResultsIn the post‐treatment liver stiffness cohort, during a mean follow‐up of 27.3 months, 21 (2.4%) developed decompensated cirrhosis, 26 (3.0%) developed HCC and 57 (6.5%) died or underwent liver transplant. Compared to patients with post‐treatment liver stiffness ≤12.5 kPa, those with post‐treatment liver stiffness >20 kPa, had higher rates of developing decompensated cirrhosis (adjusted HR 3.85, 95% CI 1.29‐11.50) and the composite outcome of death, liver transplant, decompensated cirrhosis or HCC (adjusted HR 1.95, 95% CI: 1.07‐3.56). There were no significant associations between pre‐treatment liver stiffness and any outcomes on multivariable analysis.ConclusionsPost‐treatment liver stiffness >20 kPa, but not pre‐treatment liver stiffness, was independently associated with the development of decompensated cirrhosis and the composite outcome in multivariable analyses. Measuring liver stiffness should be considered after anti‐viral treatment because it predicts adverse outcomes even beyond routinely available clinical predictors.