Antiferroelectrics with excellent energy storage density have attracted considerable attention due to their potential applications in electric vehicles, pulsed power weapons, etc. With the trend of environmental protection, the lead-free antiferroelectric AgNbO3 is a promising candidate for energy storage applications. However, the limited recoverable energy density (Wrec) of AgNbO3 severely restricts its application in high-power systems. To enhance the Wrec of AgNbO3, the A/B-site Sm3+/Hf4+ co-doping approach was adopted. It positively influenced the energy density and efficiency in AgNbO3 by simultaneously increasing the maximum polarization and breakdown strength. The optimized Wrec of 1.98 J/cm3 and high energy storage efficiency () of 64% were obtained in the MnO2-doped Ag0.97Sm0.01Nb0.99Hf0.01O2.995 ceramic at an electric field of 202 kV/cm. This work indicates that the A- and B-site substitution with donor and acceptor dopants and using MnO2 as a sintering aid is an effective strategy for developing high-performance ceramic capacitors for energy storage applications.