Eosinophilic myocarditis (EM) is a rare, potentially life-threatening, form of inflammatory heart disease characterized by eosinophilic infiltration of the myocardium. Different diseases are involved in its etiopathogeneses, such as eosinophilic granulomatosis with polyangiitis (or Churg-Strauss Syndrome), hypereosinophilic syndromes, parasitic infections, drug reactions, paraneoplastic syndromes and primary immunodeficiencies (e.g. Omenn Syndrome). There is a wide spectrum of clinical pictures at presentation ranging from chronic restrictive cardiomyopathy (Loeffler cardiomyopathy) to acute necrotizing myocarditis with cardiogenic shock. The genetic contribution and the environmental interplay, such as SARS-CoV-2 infection and related vaccines, are fields not well studied yet. Many non-invasive tools, mainly echocardiography and cardiac magnetic resonance imaging, along with invasive procedures, such as endomyocardial biopsy, are the crucial steps in the diagnostic workup. The correct diagnosis is a challenge but mandatory for timely and appropriate immunosuppressive therapy.