Both parkin (an E3 ubiquitin ligase) and PINK1 (a PTEN-induced putative kinase 1), master regulators of mitophagy, undergoes the degradation of excess mitochondria to maintain cellular homeostasis. Although parkin and PINK1 are expressed in the heart, its pathophysiological role remains unknown. Here, we found that phosphorylation level of parkin at serine 65 was up-regulated, regardless of decreased level of total parkin protein in cardiomyocytes excised from dilated cardiomyopathy (DCM) mice compared to control mice. Also, both parkin and PINK1 bound to phospholamban (PLN), a potent inhibitor of sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA2a), in cardiomyocytes excised from DCM mice tighter than control mice. Furthermore, we observed that the expression level of PLN was decreased in parkin overexpressing HEK293 cells, whereas knockdown of parkin increased PLN expression level in HEK293 cells. These data indicate that PLN may be one of the substrates for parkin, and is degraded via parkin-mediated polyubiquitination in failing hearts. Future work is necessary to determine whether parkin can regulate cardiac function in different stages of DCM especially through its role in regulating PLN levels.