AgNbO₃-based ceramics have been widely studied as ideal lead-free materials. Herein, AgNbO₃:xCeO₂ (x = 0, 1, 2 mol%) ceramics were successfully prepared by the conventional solid-state reaction method. The optimization of energy storage properties is ascribed to the enhanced antiferroelectric (AFE) stability and the increased breakdown strength (E_b). The reduction of the tolerance factor leads to the enhancement of AFE stability. In addition, the enhancement of E_b is due to the increase of actual density, which is achieved through the regulation of CeO₂ amount and grinding procedure in the experimental process. A high recoverable energy density (W_rec) of 5.04 J/cm³ and an energy efficiency (η) of 46.2% were achieved in AgNbO_3:0.01CeO₂ ceramics under an applied electric field up to 390 kV/cm. A higher η of 55.4% was obtained in AgNbO₃:0.02CeO₂ components. This research provides guidance for finding ceramic materials with comprehensive energy storage properties.