It is generally believed that a mechanical signal initiates a cascade of biological events leading to coordinated cardiac remodeling. 14-3-3 family members are dimeric phosphoserine-binding proteins that regulate signal transduction, apoptotic, and checkpoint control pathways. To evaluate the molecular mechanism underlying swimming stress-induced cardiac remodeling, we examined the role of 14-3-3 protein and MAPK pathway by pharmacological and genetic means using transgenic mice with cardiac-specific expression of dominant-negative (DN) mutants of 14-3-3 (DN14-3-3 or TG) and p38 and MAPK (DNp38andDNp38). p38 MAPK activation was earlier, more marked and longer in the myocardium of TG group compared to the non-transgenic (NTG) group after swimming stress, while JNK activation was detected on day 5 and decreased afterwards. In contrast, extracellular signal-regulated kinase (ERK) 1/2 was not activated after swimming stress in either groups. Cardiomyocyte apoptosis, cardiac hypertrophy and fibrosis were greatly increased in the TG group compared to the NTG group. Moreover, we found a significant correlation between p38 MAPK activation and apoptosis in the TG group. Furthermore, DN14-3-3 hearts showed enhanced ANP expression. In contrast, DNp38 and DNp38 mice exhibited reduced mortality, and increased resistance to cardiac remodeling after 28 days of swimming stress compared to TG and NTG mice. Besides, treatment with a p38 MAPK inhibitor, FR167653, resulted in regression of cardiac hypertrophy and fibrosis and improvement in the survival rate in TG group. These results indicate for the first time that 14-3-3 protein along with p38 MAPK plays a crucial role in left ventricular remodeling associated with swimming stress.