We performed cardiac resynchronization therapy (CRT) in addition to mitral valve replacement (MVR) in a 66-year-old patient with dilated cardiomyopathy (DCM) associated with complete left bundle branch block (CLBBB) and mitral valve insufficiency. Tissue Doppler echocardiography showed synchronicity of the septum and lateral wall in the left ventricle after CRT. New York Heart Association functional class improved from III to I after CRT and MVR. CRT of the dyssynchronic myocardium in a patient with DCM associated with CLBBB improves regional cardiac function and synchronicity.