Aim To demonstrate the mechanisms of proteasome inhibition on norepinephrine （NE）-induced hypertrophic growth of neonatal rat cardiomyocytes（NRC） via studying the alteration of calcineurin（CaN） signaling pathway.Methods Proteasome inhibitor MG262 was cotreated with NE in NRC. Cell size was observed by phalloidin-stained technique. The expression of fetal genes and CaN was detected by using RNA dot blot analysis and Western blot analysis respectively. The fixed cells were immunofluorescence labeled with nuclear factor of activated T cell c4 （NFATc4） and visualized by fluorescence microscopy. Results Fetal genes of atrial natriuretic factor （ANF）, brain natriuretic peptide （BNP） and β-myosin heavy chain （β-MHC） mRNA as well as expression of CaN were upregulated and NFATc4 was predominantly expressed in nucleus on NE induced NRC. However, more than 2.1 fold NE-induced increase in cardiomyoctyes was markedly supressed by cotreatment with MG262（P<0.05）. NE-induced upregulation of CaN and fetal gene expression was significantly relieved by MG262（P<0.05）. NFATc4 was relocated from nucleus to cytoplasm. Conclusion MG262 attenuates agonist induced cardiomyocyte hypertrophy, at least in part, via inhibiting CaN signaling pathway.