Aims This study assessed the budget impact of resmetirom as a treatment for adults with non-cirrhotic non-alcoholic steatohepatitis (NASH) with moderate-to-advanced liver fibrosis and estimated total costs for a hypothetical private payer in the United States. Materials and methods A three-year budget impact analysis based on an open cohort state transition model was developed for a hypothetical one-million-member private health plan. The comparator was Standard of Care (SOC), defined as routine care for non-cirrhotic NASH patients with moderate-to-advanced liver fibrosis. Each year, the number of resmetirom treatment-eligible patients was estimated through prevalent, incident, and diagnostic rate estimates. Costs included resources incurred by the medical and pharmacy benefits of private payers, including resmetirom drug acquisition costs, diagnosis and monitoring, other medical and other prescription costs stratified by disease progression status (i.e. non-cirrhotic vs. cirrhotic/advanced liver diseases). Resmetirom adverse event management costs were included in sensitivity analysis. Drug costs were estimated based on the average wholesale acquisition cost as of March 2024. Other costs were based on published sources and inflated to 2023 US dollars. Budget impact outcomes were presented in aggregate, net, and on a per-member per-month (PMPM) basis. Results Compared with a scenario without resmetirom, the introduction of resmetirom yielded results ranging from 50 to 238 treated patients, net budget impact of $2.2 to $9.5 million, and PMPM from $0.19 to $0.80 over years one and three. Net costs excluding resmetirom declined over time. In sensitivity analyses, results were most sensitive to diagnostic and epidemiologic inputs. Limitations Market shares are based on internal forecasts, a short time horizon, average treatment effects, and other limitations common to BIMs. Conclusion The adoption of resmetirom on the formulary for the treatment of non-cirrhotic NASH with moderate-to-advanced liver fibrosis resulted in a moderate increase in budget impact with declining costs related to NASH progression.