An amino acid exchange (P209L) in the HSPB8 binding site of the human cochaperone Bcl2-associated athanogene 3 (BAG3) gives rise to severe dominant childhood cardiomyopathy. To phenocopy the disease in mouse and gain insight into its mechanisms, we have generated humanized transgenic mouse models. Expression of human BAG3P209L-eGFP in mice caused Z-disc disintegration and formation of protein aggregates containing BAG3, components of the Z-disc, and the protein quality control system in cardiomyocytes. This was accompanied by massive fibrosis resulting in a severe, early-onset restrictive cardiomyopathy with increased mortality, as observed in patients. Here we present the shotgun proteome data of mice expressing hBAG3P209L-eGFP compared to control.