Antiferroelectric (AFE) materials are promising for the applications in advanced high-power electric and electronic devices. Among them, AgNbO₃ (AN)-based ceramics have gained considerable attention due to their excellent energy storage performance. Herein, multiscale synergistic modulation is proposed to improve the energy storage performance of AN-based materials, whereby the multilayer structure is employed to improve the breakdown strength (E_b), and Sm/Ta doping is utilized to enhance the AFE stability. As a result, ultrahigh recoverable energy storage density (W_rec) up to 15.0 J·cm⁻³ and energy efficiency of 82.8% are obtained at 1500 kV·cm⁻¹ in Sm/Ta co-doped AN multilayer ceramic capacitor (MLCC), which are superior to those of the state-of-the-art AN-based ceramic capacitor. Moreover, the discharge energy density (W_d) in direct-current charge–discharge performance reaches 9.1 J·cm⁻³, which is superior to that of the reported lead-free energy storage systems. The synergistic design of composition and multilayer structure provides an applicable method to optimize the energy storage performance in all dielectric energy storage systems.