This work studies the influence of the mechanical and electrical constraint on the dielectric and mechanical breakdown of alumina ceramics (Al2O3). In this study the dielectric and mechanical breakdown of alumina with different thickness has been characterized and compared with the results obtained with the electromechanical setup. It can be observed that the mechanical prestress of 50% of the mechanical breakdown value, applied to the samples reduces the dielectric breakdown field of the sample of 12%. A similar behavior is observed for the electrical prestress, for 70% of the dielectric breakdown field on the mechanical breakdown strength, resulting a reduction of 30% of the mechanical breakdown strength.