ObjectiveThe study objective was to determine factors associated with obtaining COVID-19 vaccination in people with co-occurring alcohol use disorder (AUD) and serious mental illness (SMI). MethodsSurvey responses were obtained from 135 adults with SMI seeking community-based AUD treatment about their primary series vaccination status, COVID-19 preventative practices, vaccination motivators, reasons for vaccine hesitancy, and strategies to increase vaccination uptake. Vaccinated and unvaccinated groups were compared. Responses to survey items with nominal or Likert scales were analyzed with chi-square tests of association. Logistic regression was employed to determine predictors of vaccine status. ResultsSeventy-nine percent (n=107) of participants reported they were vaccinated. A higher proportion of vaccinated participants believed COVID-19 was a serious disease. While both groups adopted preventative hygiene practices at similar rates (e.g., washing hands), vaccinated participants engaged in more interpersonal practices directly involving others (e.g., wearing masks and avoiding crowds). The strongest vaccine motivator was protecting personal health, while the primary reason for hesitancy was potential side effects. Most unvaccinated participants endorsed increased safety information availability (61.1 %) and living with a high-risk-for-severe-infection individual (55.6 %) as reasons to overcome hesitancy. ConclusionsVaccination rates, motivators, and hesitancy reasons were similar to the general United States population. Strategies to increase vaccination in this high-risk population should include education on vaccine safety and side effects and the impacts of COVID-19 and other respiratory illnesses on others.