SUMMARY OBJECTIVE: This study aims to know the main determinants of hesitation to the vaccine against COVID-19 mentioned by medical students in Brazil. METHODS: A cross-sectional study with 250 students who answered the online questionnaire between December 18, 2020 and January 8, 2021. RESULTS: Most students (84%) mentioned the intention to take anti-COVID vaccine and 14% were hesitant. Information provided by governments (59.2%), the pharmaceutical industry (54.4%), and the press (51.6%) were the items that most generated vaccine hesitation. CONCLUSION: In the context of the COVID-19, vaccine hesitation is an additional concern because adherence to vaccination is a recurring challenge. The category of contextual influences predominated among the main determinants of anti-COVID vaccine hesitation expressed by medical students in Brazil, disfavoring vaccine adherence in this public.