A newborn was suspected of having situs inversus with levocardia based on chest X-ray. Echocardiography ruled out this hypothesis but revealed a giant cardiac mass that was confirmed by magnetic resonance imaging. Coronary angiography showed that the right coronary artery ran on the surface of the mass, and only partial debulking surgery was performed to relieve right heart compression. Histological examination classified the mass as cardiac fibroma. Complex diagnostic work-up allowed correct anatomic definition of the mass as well as its relationship with adjacent structures, and helped guide surgical planning.