Abstract: Objective To explore nicotinamide phosphoribosyltransferase (NAMPT) expression in dilated cardiomyopathy (DCM) and its initial mechanism in the pathogenesis of DCM. Methods The peripheral blood of 131 Chinese patients with DCM confirmed by West China Hospital of Sichuan University during 2010-2013 were collected. 137 cases of Chinese Han healthy persons who were randomly selected in the physical examination center of West China Hospital of Sichuan University as the control group. The serum NAMPT levels were measured by ELISA. The NAMPT mRNA levels were determined by RT-PCR. Plasmids over-expressing NAMPT and empty vector were constructed and transfected into H9C2 cells. By using WST-1 technique, cell cycle detection and flow cytometry measurements, the effect of NAMPT on H9C2 proliferation and apoptosis was studied. Results Serum NAMPT level was significantly higher in the DCM group compared with that of controls and positively associated with the grade of heart failure and the size of left ventricular in DCM patients. The NAMPT mRNA level was significantly lower in the DCM group than that in the control group. The plasmid over-expressing NAMPT promoted H9C2 cells proliferation and increased the proportion of S phase cells compared with that of empty plasmid group. Over-expressing NAMPT increased proportion of the viable cells and reduced the proportion of late apoptotic and necrotic cells than empty plasmid group in the basic situation or after being treated with different concentrations of H₂O₂. Conclusion The high expression of plasma protein level of NAMPT while low expression of NAMPT mRNA in peripheral blood cells, contributes one of the biological characteristics to DCM. The decrease of intracellular NAMPT may be an important factor in the pathogenesis of DCM.