Acute mitral regurgitation associated with rupture of papillary muscle is a rare complication of blunt chest trauma. Echocardiographic information is very useful in the diagnosis of papillary muscle rupture, evaluation of left ventricular function and other abnoramlity of heart. The value of transthoracic echocardiography in blunt chest trauma is limited because patients with severe chest wall injury often have suboptimal echocardiographic fingings. But transesophageal echocardiography can provide high quality images when the transthoracic echocardiographic image quality is poor. We report 27 year-old female with papillary muscle rupture after blunt chest trauma in whom transthoracic echocardiography could not provide a prompt diangosis, but definitive evidence of papillary muscle rupture was demonstrated by transesophageal echocardiography.