In December 2020, the Ministry of Health in Israel approved the Pfizer-BioNTech mRNA vaccine (BNT162b2) for prevention of COVID-19 disease shortly after the Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for it. Shortly thereafter, during a three-week period between January 30th and February 20th 2021, six men were hospitalized in our department with myocarditis after receiving the vaccine. Five patients presented 24–72 hours after receiving the second dose of the vaccine and one patient presented 16 days after receiving the first dose of the vaccine. All patients were COVID-19 RT-PCR negative and non-reactive for anti-nucleocapsid protein antibodies. All patients responded to the vaccine as evidenced by being positive for antibodies against the spike protein. Further laboratory testing included a complete blood count, complete metabolic panel, troponin, C-reactive protein, and PCR testing and serological determination of antibodies against common infectious pathogens related to myocarditis. To the best of our knowledge, we were the first ones in the world to report the adverse reaction of myocarditis after BNT162b2 vaccination.