The aim of the study was to investigate serum global proteomes in dogs with overt dilated cardiomyopathy (DCM) and to evaluate protein expression in serum with that in ascitic fluid. Eight healthy dogs (control group) and 8 dogs with DCM were included in the study. DCM was diagnosed based on echocardiographic evidence including increased left ventricular dimension at diastole and systole, increased E point to septal separation, and decreased fractional shortening. Serum and ascitic fluid samples were analyzed for proteomes using a label-free LC-MS/ MS method. Proteome analyses revealed significantly different expressions of eight proteins in all samples. Expressions in serum of apolipoprotein (Apo) A1, Ig heavy chain V, superoxide dismutase and plasminogen were higher (P<0.001), while expressions of clusterin, hemoglobin subunit beta, Apo-CII, and beta 2 glycoprotein I (beta 2GPI) were lower (P<0.001) in dogs with DCM than in control dogs. In addition, Apo-A1, clusterin, hemoglobin subunit beta, Ig heavy chain V, plasminogen and beta 2GPI were down-regulated whereas Apo-CII and superoxide dismutase were up-regulated in ascitic fluid compared with serum in dogs with DCM. Data obtained in the present study suggest that serum and/or ascitic fluid proteomes may explain some of the pathophysiological mechanisms involved in the progression of DCM.