Traumatic aorto-right ventricular fistulas are rare lesions after penetrating thoracic injuries. Although aorto-right ventricular fistulas are well tolerated initially, most of them result in heart failure over a variable period. Penetrating cardiac trauma cases often need prompt cardiac surgery that does not allow further and detailed imaging methods for early diagnosis of lesions such as intracardiac defects and intracardiac fistulas. In this article, we report a case of aorto-right ventricular outflow tract fistula after a stab wound that was diagnosed on the second day after first successful surgery for acute tamponade.