Abstract The authors report the case of a 53-year-old man, with a long-standing history of mild mitral stenosis, admitted for worsening fatigue. Transthoracic echocardiography (limited by poor image quality) showed mitral annular calcification, leaflets that were difficult to visualize and an estimated mitral valve area of 1.8 cm2 by the pressure half-time method. However, elevated mean transmitral and right ventricle/right atrium gradients were identified (39 and 117 mmHg, respectively). This puzzling discrepancy in the echocardiographic findings prompted investigation by transesophageal echocardiography, which revealed an echogenic structure adjacent to the mitral annulus, causing severe obstruction (effective orifice area 0.7 cm2). The suspicion of supravalvular mitral ring was confirmed during surgery. Following ring resection and mitral valve replacement there was significant improvement in the patient's clinical condition and normalization of the left atrium/left ventricle gradient. Supravalvular mitral ring is an unusual cause of congenital mitral stenosis, characterized by an abnormal ridge of connective tissue on the atrial side of the mitral valve, which often obstructs mitral valve inflow. Few cases have been reported, most of them in children with concomitant congenital abnormalities. Diagnosis of a supravalvular mitral ring is challenging, since it is very difficult to visualize in most diagnostic tests. It was the combination of clinical and various echocardiographic findings that led us to suspect this very rare condition, enabling appropriate treatment, with excellent long-term results.