BackgroundKounis syndrome is a rare clinical condition characterized by the occurrence of an acute coronary event induced by an acute allergic episode. The ongoing pandemic of coronavirus disease 2019 (COVID-19) has contributed to an increase in the incidence of allergic reactions to a certain extent, thereby increasing the incidence of Kounis syndrome. Timely diagnosis and effective management of this disease are important in clinical practice.Case presentationWe report a 43-year-old woman who developed generalized pruritus, breathlessness, paroxysmal precordial crushing pain, and dyspnea after receiving the third dose of the COVID-19 vaccine. After anti-allergic treatment and therapy for acute myocardial ischemia, her symptoms resolved with improvement in cardiac function and resolution of ST-segment changes. The prognosis was satisfactory, and the final diagnosis was type I Kounis syndrome.ConclusionThis patient with type I Kounis syndrome rapidly developed acute coronary syndrome (ACS) after an acute allergic reaction to the COVID-19 vaccine. ​Timely diagnosis of acute allergic reaction and ACS, and targeted treatment based on the relevant guidelines are the key to successful treatment of the syndrome.​