Clinical trials of the COVID-19 vaccine reported the safety and efficacy of mRNA vaccines (AstraZeneca) to help control the disease. Few previous reports have shown various side effects associated with COVID-19 vaccines that vary in severity. The possibility of pericarditis and myocarditis has been observed in people who have received an mRNA COVID-19 vaccine which we are reporting. Acute inflammatory pericarditis can be a rare presentation after receiving the first dose of this vaccine, and it is enriching to share such rare presentations in the era of COVID-19 for better management and outcomes after vaccination. . This is a case of acute inflammatory pericarditis with a small pericardial effusion after receiving the first dose of AstraZeneca COVID-19 vaccine in a healthy adult patient who had no other symptoms suggestive of other viral illness in addition to the negative COVID-19 PCR. A 48-year-old healthy male presented nine days after receiving the first dose of COVID-19 AstraZeneca vaccine. The symptoms started three days after the vaccine, when he complained of progressive retrosternal chest pain with low-grade fever and generalized fatigue, followed by exertional dyspnea after a few days. The diagnosis of acute inflammatory pericarditis with small pericardial effusion was established, and the patient was accordingly treated. One week later, the patient showed significant clinical improvement with the resolution of his pericardial effusion. After 39 days, there was a significant radiological resolution of signs of acute pericarditis.