Both high thermal conductivity and high electrical resistivity of immiscible poly(vinylidene fluoride) (PVDF)/polystyrene (PS) 30/70 blends are achieved by controlling the localization of hybrid fillers of multi-walled carbon nanotubes (MWCNTs) and silicon carbide (SiC) nanoparticles. The selective localization of both fillers in the minor phase of PVDF by using the masterbatch technique is confirmed by the scanning electron microscopy (SEM) observation. The domain size of the PVDF phase can be significantly reduced by further adding the fillers. The percolation threshold of MWCNTs in PVDF/PS 30/70 blend is measured to be ca. 2.9 vol% with respect to the whole system. Compared with the case where only MWCNTs or SiC nanoparticles are present in the PVDF phase, the selective localization of both fillers in the PVDF phase can yield higher thermal conductivity and higher alternating current (AC) resistivity. Such materials could have potential applications in the electronic industry.