OBJECTIVES: The aim of this cross-sectional study was to investigate the determinants of COVID-19 vaccine acceptance in University of Defence members. BACKGROUND: Vaccination is the most important method of prevention against COVID-19 and achieving suffi cient vaccination rate is thus essential to maintain the military capability. METHODOLOGY: An online questionnaire was distributed electronically to 2,408 respondents in autumn 2021. The survey was designed to collect demographic predictors of vaccination, data on motivation and reasons for refusing vaccination. RESULTS: A total of 626 completed questionnaires were analyzed, of which 557 (89 %) were vaccinated and 69 (11 %) were unvaccinated respondents. The most signifi cant predictors of vaccine acceptance were: concern about COVID-19 (OR 2.44, p < 0.001), history of COVID-19 (OR 0.39, p = 0.001). The most frequently cited motives for vaccination were health protection (74.7 %) and an easier social life (69.1 %), while concerns about vaccine safety and vaccine adverse effects (79.1 %) followed by lack of confi dence in vaccine effi cacy (68.7 %) were the main reasons for vaccine refusal. CONCLUSION: To increase the vaccination rate it is necessary to target the younger population and increase awareness of vaccine safety and effi cacy. If these measures are not suffi cient to encourage voluntary vaccine acceptance, consideration should be given to making vaccination mandatory for selected professional groups