Ebstein's anomaly (EA) is primarily diagnosed by echocardiography. The purpose of this study was to compare echocardiography and magnetic resonance imaging (MRI) in EA. Data from cardiac MRI and echocardiography were prospectively collected from 16 patients with EA. Imaging data also were compared with intraoperative findings. Information provided by MRI and echocardiography were comparable for left ventricular size and function, tricuspid valve repairability, qualitative assessment of right-sided cavities, and visibility of septal and anterior tricuspid valve leaflets. The posterior tricuspid valve leaflet and tricuspid valve fenestrations were better visualized with MRI; associated heart defects were equally recognized, apart from small shunts that tended to be more readily diagnosed with echocardiography. Quantification of right-cavity size and right ventricular ejection fraction was possible only with cardiac MRI. The degree of tricuspid valve regurgitation was underestimated by echocardiography (2 patients) and by MRI (4 patients) when compared with intraoperative assessment. When evaluating EA, echocardiography and MRI provide complementary data. For visualization of the posterior tricuspid valve leaflet and quantitative assessment of right ventricular size and function, MRI is preferable. For appropriate risk stratification in EA, both MRI and echocardiography should be performed before cardiac surgery.