As marijuana, the most widely-used illicit drug in adolescents and adults, has some unknown side effects, marijuana abuse has become a public health concern. Also, marijuana affects different organs such as heart in its rate, rhythm and coronary flow; it eventually leads to events such as myocardial infarction and rarely myocarditis. A 24-year-old man without any medical history or cardiovascular risk factors presented with chest pain after marijuana consumption. Based on electrocardiogram, myocardial cytolysis and transthoracic echocardiography acute myocarditis diagnosis was established. A few days later, transthoracic echocardiography showed a small clot in apex with reduced left ventricle ejection fraction, in the absence of local akinesia. The patient was discharged with oral anticoagulant stable and without any symptoms. The myocarditis after marijuana abuse is rare. The physicians should include acute myocarditis in differential diagnosis of a patient with chest pain after using marijuana.