In this study, 0.2875 Pb(Mg1/3Nb2/3)O3–0.2875 Pb(Yb1/2Nb1/2)O3–0.425 PbTiO3 (0.2875PMN–0.2875PYbN–0.425PT) ternary ceramic composition was doped with 1 mol% MnCO3 in order to induce hard character for potential high-power applications. Dense 0.2875PMN–0.2875PYbN–0.425PT ceramics with 1 mol% MnCO3 addition were fabricated after sintering at 1100 °C. εr = 1728, tanδ = 0.35 %, d33 = 320 pC/N, d31 = −103 pC/N, Qm = 467, kp = 0.40, k31 = 0.24, k33 = 0.49, and Tc = 280 °C were measured for Mn-doped ceramics. However, undoped ceramics had εr = 2380, tanδ = 1.95 %, d33 = 433 pC/N, d31 = −145 pC/N, Qm = 60, kp = 0.43, k31 = 0.27, k33 = 0.48, and Tc = 285 °C. Acceptor Mn2+/Mn3+ ions presumably substituted B-site ions in the perovskite structure and formed defect dipole pairs. The electrically “hard” character was induced as a result of the domain wall pinning due to the existing defect pairs. Particularly, increasing Qm from 60 to 467 and decreasing tanδ from 1.95 to 0.35 % after Mn doping showed that Mn-doped 0.2875PMN–0.2875PYbN–0.425PT ceramics with “hard” character are potential candidates for high-power projector and transducer applications.