Importance Persons with opioid use disorder (OUD) and co-occurring alcohol use disorder (AUD) are understudied and undertreated. It is unknown whether the use of medications to treat OUD is associated with reduced risk of alcohol-related morbidity. Objective To determine whether the use of OUD medications is associated with decreased risk for alcohol-related falls, injuries, and poisonings in persons with OUD with and without co-occurring AUD. Design, Setting, and Participants This recurrent-event, case-control, cohort study used prescription claims from IBM MarketScan insurance databases from January 1, 2006, to December 31, 2016. The sample included persons aged 12 to 64 years in the US with an OUD diagnosis and taking OUD medication who had at least 1 alcohol-related admission. The unit of observation was person-day. Data analysis was performed from June 26 through September 28, 2020. Exposures Days of active OUD medication prescriptions, with either agonist (ie, buprenorphine or methadone) or antagonist (ie, oral or extended-release naltrexone) treatments compared with days without OUD prescriptions. Main Outcomes and Measures The primary outcome was admission for any acute alcohol-related event defined by International Classification of Diseases, Ninth Revision and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes. Conditional logistic regression was used to compare OUD medication use between days with and without an alcohol-related event. Stratified analyses were conducted between patients with OUD with and without a recent AUD diagnostic code. Results There were 8 424 214 person-days of observation time among 13 335 participants who received OUD medications and experienced an alcohol-related admission (mean [SD] age, 33.1 [13.1] years; 5884 female participants [44.1%]). Agonist treatments (buprenorphine and methadone) were associated with reductions in the odds of any alcohol-related acute event compared with nontreatment days, with a 43% reduction for buprenorphine (odds ratio [OR], 0.57; 95% CI, 0.52-0.61) and a 66% reduction for methadone (OR, 0.34; 95% CI, 0.26-0.45). The antagonist treatment naltrexone was associated with reductions in alcohol-related acute events compared with nonmedication days, with a 37% reduction for extended-release naltrexone (OR, 0.63; 95% CI, 0.52-0.76) and a 16% reduction for oral naltrexone (OR, 0.84; 95% CI, 0.76-0.93). Naltrexone use was more prevalent among patients with OUD with recent AUD claims than their peers without AUD claims. Conclusions and Relevance These findings suggest that OUD medication is associated with fewer admissions for alcohol-related acute events in patients with OUD with co-occurring AUD.