Cardiac dysfunction is involved in disorders of energy metabolism. High‐titre autoantibodies against the β1‐adrenoceptor (β1‐AAs) have been reported to exist in patients with cardiac dysfunction; however, the mechanism by which β1‐AAs affect cardiac function is unknown. This study aimed to determine whether β1‐AAs disturb myocardium energy metabolism and cause cardiac dysfunction. β1‐AA monoclonal antibodies (β1‐AAmAbs) were successfully pre‐synthesized by hybridoma clones and used in all experiments. β1‐AAmAbs impaired cardiac function and induced a myocardial metabolic disturbance, as evidenced by decreased left ventricular ejection fraction and fractional shortening. In addition, β1‐AAmAbs decreased the adenosine triphosphate level and increased cardiac energy consumption (rate–pressure product). We further showed that the effects of β1‐AAmAbs on heart tissue might involve the mitochondria and metabolic pathways via the β1‐adrenoceptor based on an immunoprecipitation and mass spectrometry. Additionally, we found that β1‐AAmAbs impaired myocardial mitochondrial structure, decreased the membrane potential, and induced insufficient mitophagy. In conclusion, β1‐AAmAb‐induced cardiac dysfunction is partly due to a disturbance in myocardial energy metabolism.