Introduction and objectives Vaccines against SARS-CoV-2 have been a major scientific and medical achievement in the control of the COVID-19 pandemic. However, very infrequent cases of inflammatory heart disease have been described as adverse events, leading to uncertainty in the scientific community and in the general population. Methods The Vaccine–Carditis Registry has included all cases of myocarditis and pericarditis diagnosed within 30 days after COVID-19 vaccination since August 1, 2021 in 29 centers throughout the Spanish territory. The definitions of myocarditis (probable or confirmed) and pericarditis followed the consensus of the Centers for Disease Control and the Clinical Practice Guidelines of the European Society of Cardiology. A comprehensive analysis of clinical characteristics and 3-month evolution is presented. Results From August 1, 2021, to March 10, 2022, 139 cases of myocarditis or pericarditis were recorded (81.3% male, median age 28 years). Most cases were detected in the 1st week after administration of an mRNA vaccine, the majority after the second dose. The most common presentation was mixed inflammatory disease (myocarditis and pericarditis). 11% had left ventricular systolic dysfunction, 4% had right ventricular systolic dysfunction, and 21% had pericardial effusion. In cardiac magnetic resonance studies, left ventricular inferolateral involvement was the most frequent pattern (58%). More than 90% of cases had a benign clinical course. After a 3-month follow-up, the incidence of adverse events was 12.78% (1.44% mortality). Conclusions In our setting, inflammatory heart disease after vaccination against SARS-CoV-2 predominantly affects young men in the 1st week after the second dose of RNA-m vaccine and presents a favorable clinical course in most cases. Graphical abstract