Eosinophilic myocarditis usually results from myocardial damage as a result of drugs or parasites, and is generally associated with increased peripheral eosinophil count. This form of myocarditis is difficult to diagnose clinically. A 25 year-old previously healthy woman was transferred from a local clinic because of hypotension and dyspnea with sudden cardiogenic shock after a three day history of gastrointestinal illness. Echocardiography revealed concentric left ventricular wall thickening with moderate pericardial effusion. Biopsy of endomyocardial tissue from the right ventricle showed diffuse infiltration of inflammatory cells, mostly eosinophils, even though the patient had a peripheral eosinophil count that was normal at the time of biopsy. The patient was treated with corticosteroids for the symptoms of pericarditis, and she recovered without cardiac sequelae, clinically and echocardiographically. We here report a case of acute eosinophilic myopericarditis, with cardiogenic shock, diagnosed by endomyocardial biopsy with normal peripheral eosinophil count at the time of biopsy, and complete recovery without sequelae.