The first case of right ventricular aneurysm caused by acute myocarditis is reported. Positive gallium-67 uptake and contrast enhancement in the gadolinium diethylenetriaminepentaacetic acid-enhanced magnetic resonance images were detected in the apical region surrounding the aneurysm, suggesting transmural myocardial inflammations in the apical portion of the heart. The aneurysm was repaired surgically, and biopsy of the right ventricular myocardium showed replacement fibrosis and inflammatory infiltrate.