A hierarchical NiO-[CdO]2 nanocomposite has been synthesized by a sol–gel auto-combustion route and characterized with a view to studying the electric field emission and conduction mechanism therein. The structural features, surface morphologies, and elemental compositions of the as-prepared samples have been characterized by XRD, Raman, FESEM, and TEM techniques. A low turn-on field (4.50 V/μm) and threshold field (5.04 V/μm) were found to be sufficient to draw emission current densities of 1 μA/cm2 and 10 μA/cm2 from NiO-[CdO]2-modified cathodes. A maximum emission current density of 121 μA/cm2 at a low applied electric field of 6.5 V/μm and long emission current stability were achieved at a preset value of 5 μA. The field enhancement factor (β) was determined as 1854 in the high-field region by computing the local work function (φ) through density functional theory (DFT), and the entire field emission (FE) performances have been compared with those of various pristine compounds. The temperature-dependent electrical conduction mechanism has been further explained with the help of impedance analysis over the temperature range 323–623 K and a wide frequency range from 5 Hz to 1 MHz. The grain and grain boundary contributions were well distinguished by impedance and a modulus formalism, with respective activation energies of Eg = 0.25–0.26 eV and Egb = 0.31–0.32 eV. The temperature-dependent frequency exponents for grains (n1) and grain boundaries (n2) demonstrate two different conduction mechanisms, namely quantum mechanical tunneling for grains, and correlated barrier hopping for grain boundaries. Maxwell–Wagner-type dielectric polarizations are explained by our experimental results, and the highest real dielectric constant (εr) 1893 was calculated at 623 K.