This case report describes cardiac manifestations in a female patient with Churg-Strauss syndrome (CSS). Cardiac magnetic resonance imaging (CMRI) is the only imaging modality able to depict cardiac involvement with endomyocardial fibrosis, myocardial edema, pericarditis associated with pericardial effusions, and apical thrombi in the left or right ventricle. The encasement of the tricuspid valve caused by an obliterating thrombus of the right ventricular cavity, as observed in our patient, is very rare. CMRI is a potentially important diagnostic tool for the early detection of dangerous cardiac complications of CSS, allowing optimal and timely therapy and reducing the comorbidity of the disease.