The temperature stability of the dielectric constant and nonlinear electrical properties of CaCu3Ti4O12 ceramics were improved by fabricating Ni2+-doped CaCu3Ti4O12/TiO2 nanocomposite ceramics. Interestingly, a large reduction of the dielectric loss to 0.009 with high epsilon' of 6314 and good temperature stability of the dielectric constant (Delta epsilon') of less than +/- 15% variation over the temperature from -60 to 210 degrees C was obtained in a CaCu2.95Ni0.05Ti4O12/TiO2 ceramic sintered at 1060 degrees C for 8 h. With these excellent properties, this ceramic is proposed for applications in high temperature X8R and X9R capacitors. Nonlinear behavior of J-E curves was observed in all CaCu3-xNixTi4O12/TiO2 ceramics that could be significantly enhanced by Ni2+ doping. Very large a (similar to 53) and E-b (similar to 15,727 V.cm(-1)) values were obtained in a CaCu2.95Ni0.05Ti4O12/TiO2 ceramic sintered at 1060 degrees C for 8 h. X-ray absorption near edge spectroscopy (XANES) was performed for verification of the Ti oxidation state of all ceramics. Microstructural and phase composition were studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD).