Sn4+-doped CaCu3Ti4O12/CaTiO3 composites were prepared using a solid state reaction method employing a simple one-step process. A minor phase of CaTiO3 grains was very well dispersed into the CaCu3Ti4O12 matrix and these two phases were clearly separated from each other in CaTiO3/CaCu3Ti4O12. The grain size of the CaCu3Ti4O12 phase was largely enhanced by Sn4+ doping. Furthermore, CaTiO3 grains were also found inside the enlarged CaCu3Ti4O12 grains. The microstructural evolution can be described based upon liquid phase sintering and the pinning effect by second-phase particles. The dielectric permittivity of Sn4+-doped CaCu3Ti4O12/CaTiO3 was greatly enhanced from similar to 2 x 10(3) to similar to 0.6-1.3 x 10(4) at 10(3) Hz, while, the dielectric loss tangent was still low. The nonlinear properties were.degraded as a main result of microstructural evolution. These results strongly indicated an extrinsic effect upon both of the giant dielectric response and nonlinear properties of CaCu3Ti4O12-based compounds. (C) 2016 Elsevier Ltd. All rights reserved.