Lead titanate (PT) ceramics co-doped with 8 to 13 mol% Ni-Nb, by substituting titanium ions, were prepared by conventional ceramic method and the influence of Ni-Nb doping level on their morpho-structural, electromechanical and dielectric properties was investigated. Dense tetragonal PT ceramics were obtained for 8 to 12 mol% Ni-Nb co-doping. Lattice anisotropy decreased from 1.053 to 1.046 with increasing doping level. Large thickness coupling factors of 0.4 were obtained for 8, 11, and 12 mol% Ni-Nb. Large electromechanical anisotropy of 10 was obtained for 8 mol% Ni-Nb. It was found that Ni-Nb co-doping has both softening and hardening effects as a function of donor or acceptor behavior of different amounts of Ni-Nb. For 13 mol% Ni-Nb, segregation of a small amount of a secondary phase occurs, lattice constants and tetragonality significantly decrease and the resulting ceramic becomes very hard.