OBJECTIVE: A microsimulation model was adapted to evaluate the cost-effectiveness of nalmefene combined with psychosocial support (NMF + PS) versus psychosocial support alone (PS). The economic impact of alcohol reduction using nalmefene treatment was not evaluated. METHOD: The model simulates patient-level alcohol consumption over a 5-year time horizon across different treatment cohorts. Study outcomes included probabilities of alcohol-attributable diseases and injuries as well as deaths from these events. The approach used nalmefene clinical trial data, a time horizon of 1 and 5 years, and a U.K. societal perspective. Extensive deterministic and probabilistic sensitivity analyses were conducted. RESULTS: Compared with the PS strategy, NMF + PS was associated at Year 5 with a gain of 0.047 quality-adjusted life years (QALYs) and an additional pound503, leading to an incremental cost-effectiveness ratio (ICER) of pound10,613 per QALY gained. When compared with the strategy without treatment, NMF + PS was associated with a gain of 0.228 QALYs and an additional pound1,795, leading to an ICER of pound1,758 per QALY gained. The NMF + PS strategy dominated both treatment strategies when considering the U.K. societal perspective. Sensitivity analyses confirmed the robustness of the results. CONCLUSIONS: A combination of NMF and PS was better than PS alone, considering a 5-year time horizon and a societal perspective.