Background: The COVID-19 pandemic and the accompanying new generation vaccines have entered our lives with many unknown effects. Method and result: This is a case report of myopericarditis diagnosed with fever and chest pain 3 days after the 2nd dose of Pfizer-BioNTech COVID-19 mRNA Vaccine in an 18-year-old man. The diagnosis was confirmed by cardiac MRI(CMR), but we presented that this diagnosis and follow-up could be made accurately with strain echocardiography(SE). Conclusion: It would be beneficial for the cardiologists who perform the primary follow-up of these patients to know that it is possible with SE to support the diagnosis and follow-up of these patients, even if CMR is not accesible.