Diffusion-induced interface migration (DIIM) is a technique for modifying the microstructure and mechanical properties of ceramics. In the present study, we investigated DIIM in 0.65Pb(Mg1/3Nb2/3)O-3.0.35PbTiO(3) (mol fraction) (PMN-PT) ceramics and its effect on mechanical properties. PMN-PT samples were fabricated using the Columbite precursor method and then surface-modified by heat treatment after packing with PbTiO3 powder to induce DIIM. Evaluation of mechanical properties using Hertzian indentation and Vickers indentation showed that the critical load for yielding and surface hardness of the PbTiO3-packed PMN-PT samples were higher than those of the unpacked samples. Thus, the mechanical properties were improved in the samples with a DIIM layer. These results showed that the reliability of mechanical properties of PMN-PT samples is improved by inducing DIIM at the surface.