In a dilated heart with impaired systolic functions, functional mitral regurgitation could be seen even in the presence of structurally normal mitral apparatus. A number of mechanisms play role in the development of functional mitral regurgitation. These are increased mitral tethering forces, reduction in closing forces and mechanical and electrical dyssynchrony. Papillary muscle dyssynchrony has also been shown to be related with functional mitral regurgitation. Cardiac resynchronization therapy is known to reduce the amount of functional mitral regurgitation in patients with left ventricular systolic failure although some may not respond to treatment with cardiac resynchronization therapy. Papillary muscle dyssynchrony may predict the response of cardiac resynchronization therapy on the regression of functional mitral regurgitation and may suggest the suitable therapeutic options, such as cardiac resynchronization therapy, mitral valve repair, coronary revascularization separately or in combination. In this review, the mechanisms of functional mitral regurgitation, papillary muscle dyssynchrony and its relationship with functional mitral regurgitation and the relationship of papillary muscle dyssynchrony with the improvement of functional mitral regurgitation after cardiac resynchronization therapy are focused.