Severe acute respiratory syndrome coronavirus 2 has spread globally. Vaccination for coronavirus disease 2019 (COVID-19) is anticipated to reduce morbidity and mortality. However, the safety of vaccines against COVID-19 is a cause for concern and uncertainty, which leads to vaccine hesitancy. There have been some self-reported questionnaire studies regarding adverse effects after COVID-19 vaccination; however, adverse effects on the oral region are rare. In this report, we present one case of ulcers arising on the bilateral palate mucosa following COVID-19 vaccination, which was suspected to be an adverse effect of vaccination.