In this research, AgNbO3 ceramics were produced by two sintering methods: reaction sintering (RS) and conventional solid-state sintering (CSSS). The process was similar for both methods, except that in RS, Ag2O and Nb2O5 precursors were mixed, then formed into pellets, skipping the calcination step, and sintered at 1100 °C for 6 hours. Both prepared ceramics had the same perovskite crystal structure with an orthorhombic crystal system and Pbcm and Pmc21 space groups with similar lattice dynamic vibration modes at room temperature. The average grain size of the polycrystalline samples prepared by RS and CSSS was found to be ∼2.03 ± 0.77 and ∼1.85 ± 0.96 μm, respectively. The relative bulk densities of the ceramics produced by RS and CSSS were found to be ∼94.0 ± 1.8 and ∼96.5 ± 1.3%, respectively. Ceramics prepared by both methods showed antiferroelectric behavior, and reaction-sintered AgNbO3 ceramics exhibited lower energy loss density than CSSS samples. In addition, a recoverable energy storage density (Wrec) of 3.1 J cm-3 and higher energy storage efficiency (η) for RS samples were measured at 175 kV cm-1. Moreover, the η values of 74.2% and 57.7% were measured for samples sintered by RS and CSSS, respectively. This energy storage efficiency is the highest ever reported for pure AgNbO3 ceramics. Furthermore, reaction-sintered samples showed good temperature stability for Wrec and η in the 30-80 °C temperature range.