Introduction Myocarditis is often an elusive diagnosis as the clinical presentation can be nonspecific and definitive diagnosis can be challenging due to the low sensitivity of endomyocardial biopsy. Additionally, treatment of myocarditis is controversial with no guidelines and limited data available regarding efficacy. Nevertheless, recent studies have demonstrated a treatment benefit with immunosuppression, particularly in giant cell myocarditis (GCM). This report highlights a unique case of histologically confirmed GCM in which the patient also had a significant peripheral hypereosinophilia, and examines the response of combined immunosuppression with rabbit anti-thymocyte globulin (RATG), corticosteroids, cyclosporine, and benralizumab–an interleukin-5 receptor antagonist–that resulted in rapid recovery. Case Report A 25 year old woman with a history of asthma for 3 years and a recent diagnosis of heart failure with reduced ejection fraction (40%) presented with acute chest pain and worsening left ventricular (LV) dysfunction with a reduction of her left ventricular ejection fraction (LVEF) to 25-30% within 2 weeks. Laboratory studies revealed a 40% peripheral eosinophilia. Further workup was negative for infection, eosinophilic granulomatosis with polyangiitis, or malignancy. A cardiac MRI showed late-gadolinium enhancement and an endomyocardial biopsy confirmed significant eosinophilic tissue infiltration, myocyte necrosis, and the presence of giant cells. She was treated with a combined immunosuppression regimen of RATG induction, corticosteroids, cyclosporine, and benralizumab. Despite this regimen, she had a recurrence of peripheral eosinophilia during the course of her hospitalization. Nevertheless, she had significant clinical improvement in symptomatology, functional status, and hemodynamics. Her peripheral eosinophilia resolved over the following days with increased corticosteroids and thereafter remained negligible. A repeat echocardiogram 3 weeks after initial initiation of immunosuppression demonstrated significant improvement in her LVEF to 53%, improvement of global strain, and reduction of left atrial dilatation. Discussion Emerging data suggests that treatment with immunosuppression can improve outcomes in patients with GCM. Indeed, this patient did have a marked improvement in LV function within 3 weeks of initiating treatment. Additionally, the use of benralizumab to treat her peripheral eosinophilia demonstrates potential implications for use in other hypereosinophilic syndromes. However, given that her serum eosinophila recurred despite being on a multi-drug immunosuppression regimen, including benralizumab, identifies potential focus areas of future research including further examination of the exact mechanism of action, the relevance of expanded use in other hypereosinophilic syndromes, and delineation of appropriate end points for measuring response.