BACKGROUND: Social determinants of health (SDOH) are becoming increasingly recognised as mediators of human health. In the setting of metabolic dysfunction-associated steatotic liver disease (MASLD), most of the literature on SDOH relates to individual-level risk factors. However, there are very limited data on neighbourhood-level SDOH in MASLD. AIM: To assess whether SDOH impact fibrosis progression in patients who already have MASLD. METHODS: This was a retrospective cohort study of patients with MASLD seen at Michigan Medicine. The primary predictors were two neighbourhood-level SDOH, disadvantage and affluence. The primary outcomes were mortality, incident liver-related events (LREs) and incident cardiovascular disease (CVD). We modelled these outcomes using Kaplan-Meier statistics for mortality and competing risk analyses for LREs and CVD, using a 1-year landmark. RESULTS: We included 15,904 patients with MASLD with median follow-up of 63 months. Higher affluence was associated with lower risk of overall mortality (hazard ratio 0.49 [0.37-0.66], p < 0.0001 for higher vs. lower quartile), LREs (subhazard ratio 0.60 [0.39-0.91], p = 0.02) and CVD (subhazard ratio 0.71 [0.57-0.88], p = 0.0018). Disadvantage was associated with higher mortality (hazard ratio 2.08 [95% confidence interval 1.54-2.81], p < 0.0001 for the highest vs. lowest quartile) and incident CVD (subhazard ratio 1.36 [95% confidence interval 1.10-1.68], p < 0.0001). These findings were robust across several sensitivity analyses. DISCUSSION: Neighbourhood-level SDOH are associated with mortality, incidence of LREs and incident CVD in patients with steatotic liver disease. Interventions aimed at disadvantaged neighbourhoods may improve clinical outcomes.