Dogs’ obesity in is a common pathology and is associated with genetic factors, feeding, housing conditions, physical inactivity. Many pathogenesis aspects of obesity development of small domestic animals are poorly studied, in particular, the development of dysfunction of the cardiovascular system is an insufficiently explored issue. The aim of this study was to study clinical, electrocardiographic, echocardiographic and biochemical parameters of blood serum of obese dogs. The objects of the study were Dachshund dogs with obesity (n = 12) and clinically healthy animals (n = 16). All animals went through a complex clinical examination, electrocardiographic, echocardiographic and laboratory studies. Parametric and nonparametric methods of statistical analysis were used in the study. It was found that dogs’ obesity is characterized by a significant increase of the respiratory rate at rest and during sleep, pulse rate, systolic, diastolic and mean arterial blood pressure. It was shown that in case of dogs’ obesity, there is a slight increase of the end-diastolic size and thickness of the free wall of the left ventricle, a shortening of the PQ interval, and voltage decrease of P, R, T deflections on electrocardiograms. There were no violations of contractility and systolic function of the left ventricular myocardium of obese dogs. It was found that the activity of alkaline phosphatase, alanine and aspartic aminotransferases, the concentration of cholesterol, triglycerides, total protein, malondialdehyde and ceruloplasmin significantly increased in blood serum of obese dogs. Dogs’ obesity does not form dogs’ syndrome of cytolysis of cardiomyocytes, as evidenced by unchanged serum activity of lactate dehydrogenase, creatine phosphokinase and cardiac troponin concentration.