Eosinophilic myocarditis is a rare form of myocardial inflammation that may lead to heart failure and death, if left untreated. A previously healthy 26-year-old man was admitted to the department with chest pain and dyspnoea, that started two days before. Few days prior to the onset of symptoms he started to take weight-loss supplement with Garcinia cambogia. On laboratory tests myocardial necrosis markers were positive and blood hypereosinophilia was noted. Left ventricular ejection fraction was slightly decreased to 45% with regional wall motion abnormalities and significantly thickened left ventricle walls. Coronary angiography did not show any abnormalities. Endomyocar dial biopsy revealed eosinophil infiltration of the myocardium. Stool cultures were positive for Giardia lamblia. The patient initially received standard heart failure therapy and then due to eosinophil infiltration of the myocardium, systemic steroids and antiparasitic treatment were added. His general condition and ejection fraction improved after a week and he was discharged home on standard heart failure treatment and prednisone. In the setting of acute coronary syndrome symptoms in patients without atherosclerotic lesions and decreased ejection fraction myocarditis should be suspected. Blood hypereosinophilia may raise suspicion of the eosinophilic myocarditis. The proper diagnosis should be supported by endomyocardial biopsy results as it plays key role in the initiation of steroid therapy which leads to heart failure symptoms relieve and improvement of left ventricle function