In this study, the temperature-dependent electro-optical properties of the nematic liquid crystal E7 in the presence of nickel oxide (NiO) nanoparticles were investigated. Birefringence variations of liquid crystal samples containing different weight percentages of NiO nanoparticles (0.01, 0.03, 0.06, 0.09, and 0.12 wt%) were measured at various temperatures. The presence of nanoparticles resulted in an increase in birefringence and an improvement in molecular ordering of the liquid crystal. The results showed that adding nanoparticles reduced the threshold voltage of the nematic liquid crystal cell. At 0.09 wt% concentration, the threshold voltage decreased by approximately 31% in the nematic phase. With increasing temperature, the threshold voltage decreased in all samples; however, this reduction was more pronounced in nanoparticle-doped samples compared to the pure one. In addition, impedance spectroscopy of the devices in the isotropic phase was performed over the frequency range of 0.1 Hz to 100 kHz to evaluate the effect of nanoparticles independent of molecular orientational order. The presence of NiO nanoparticles increased electrical conductivity and significantly affected ion transport dynamics, including ion mobility and diffusion coefficient. The simultaneous improvement in electrical and electro-optical properties demonstrates the strong potential of NiO-doped liquid crystal systems for advanced optoelectronic applications.