Background Abstinence has historically been considered the target outcome for alcohol use disorder (AUD) treatment, yet recent work has found drinking reductions after AUD treatment, as measured by World Health Organization (WHO) risk drinking levels, are associated with meaningful improvements in functioning, physical health, and quality of life. Objectives This study extends previous analyses of AUD treatment outcomes by estimating the association between changes in WHO risk drinking levels (very high, high, medium, and low, based on average daily alcohol consumption) and healthcare costs. Methods Secondary data analysis of the COMBINE study, a multisite randomized clinical trial of acamprosate, naltrexone and behavioral interventions for AUD. Generalized gamma regression models were used to estimate relationships between WHOrisk drinking level reductions over the course of treatment and healthcare costs in the year after treatment (N = 964) and up to 3 years following treatment (N = 651). Results SustainedWHOrisk drinking reductions of 2 or more levels throughout treatment were associated with 52.0% lower healthcare costs (P < 0.001) in the year following treatment, and 44.0% lower costs (P < 0.0025) over 3 years. A reduction of exactly 1 level was associated with 34.8% lower costs over 3 years, which was not significant (P = 0.05). Cost reductions were driven by lower inpatient behavioral health and emergency department utilization. Conclusions Reduction in WHO risk drinking levels of at least 2 levels was associated with lower healthcare costs over 1 and 3 years. Our results add to literature showing drinking reductions are associated with improvement in health.