Conductive polymer composites based on nanostructured particular fillers have many important applications, such as temperature and pressure sensors. Among many factors, the microstructure of conductive particle network determines the electron conduction properties. It has been found that nanospiky Ni particles filled in a polymer matrix can enable a reversible and rapid response and a large change of conductivity upon temperature change. While it has been previously hypothesized that quantum tunneling plays an important role, no direct experimental evidence with systematic characterization and understanding is available. Herein, impedance spectroscopy and low‐temperature electrical measurements are used to reveal the charge transport mechanisms of nanospiky Ni‐based nanocomposites upon temperature change. The results show that quantum tunneling effects indeed play a major role, which enables significant interparticle resistance change upon slight change (expansion and contraction) of the microstructured particle network. Pyroresistive polymer composites, composed of a polymeric matrix with nanostructured fillers, allow extremely high thermoresponsivity. Impedance spectroscopy and low‐temperature measurements reveal the charge transport mechanisms of nanospiky Ni‐based nanocomposites identifying quantum tunneling effects, which enable significant interparticle resistance changes upon slight expansion or contraction of the microstructured particle network.