Abstract Body: Introduction: Dilated cardiomyopathy (DCM) is characterized by left ventricular dilatation and systolic dysfunction, often accompanied by extensive cardiac fibrosis. Programmed cell death 5 (PDCD5) is highly expressed in adult cardiomyocytes and is known to be involved in cell survival and stress responses. However, its specific mechanistic role in the progression of DCM remains largely uncharacterized. Hypothesis: We hypothesized that PDCD5 exerts dual regulatory roles in the nucleus and cytoplasm to maintain cardiac structural integrity and limit fibrotic progression in DCM. Aims: This study aimed to investigate the cytoplasmic and nuclear functions of PDCD5 in DCM pathogenesis using mouse models and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Methods: Cardiac function in mice was evaluated via wireless electrocardiography and echocardiography. Calcium imaging and microelectrode arrays were utilized for hiPSC-CM analysis. Molecular interactions were identified using immunoprecipitation, proximity ligation assays, and chromatin immunoprecipitation. Human DCM tissue expression was quantified using immunohistochemistry. Results: At 30 weeks, PDCD5 conditional knockout (cKO) mice demonstrated significant left ventricular dilation and impaired systolic function compared to controls. Dystrophin mRNA expression was significantly reduced in these models relative to other cytoskeletal genes. Mechanistic analysis revealed that nuclear phosphor-PDCD5 regulates dystrophin transcription through interaction with the serum response factor (SRF). In the cytosol, PDCD5 knockdown induced Smad1/5 phosphorylation and mediated an interaction with ABL1, leading to the upregulation of connective tissue growth factor. Furthermore, PDCD5 double knockout (dKO; PDCD5 cKO with mdx mutant) mice exhibited a significantly shortened lifespan, dying approximately 15 weeks earlier than mdx mice, with a more severe DCM phenotype. Conclusions: Our findings indicate that PDCD5 is a critical regulator of cardiac function, interacting with SRF in the nucleus and ABL1 in the cytosol to prevent DCM progression. These results suggest that PDCD5 represents a promising therapeutic target for treating dilated cardiomyopathy.