Aneurysm of the sinus of Valsalva is a rare cardiac condition, which could be either acquired or congenital. The most frequent complication is a rupture into right cavities or more rarely into left cavities or pericardium. Rupture could be either asymptomatic or poorly tolerated with hemodynamic instability, acute heart failure or sudden death. We report the case of a 24-year-old patient with no past medical history presenting with a partially ruptured sinus of Valsalva into the pericardium and in whom the initial diagnosis was idiopathic pericardial effusion; we describe diagnostic modalities and management.