Coronavirus infectious disease 2019 infection in children and adolescents causes mild symptoms, but some may require hospitalization or Intensive care unit treatment. Therefore, the importance of vaccinating children and adolescents against COVID-19 is emphasized. However, various side effects related to the heart after COVID-19 mRNA vaccination have been reported. In one study, 227 out of 243 patients were diagnosed with myocarditis, 7 with pericarditis, and 4 with Takotsubo cardiomyopathy. One case report showed paroxysmal tachycardia developed after receiving the AstraZeneca COVID-19 vaccine in a male with previous history of paroxysmal tachycardia. In this report, we present a case of paroxysmal tachycardia after second dose of Pfizer COVID-19 vaccine without any previous history of cardiac problems. The cardiovascular complications as a side effect of COVID-19 vaccination are rare but can be fatal. Therefore, it is necessary to remain vigilant and monitor adverse reactions that may occur with the COVID-19 vaccine.