Carbon black (CB), carbon nanotubes (CNTs), and graphene nanoplatelets (GnPs) individually or doubly served as reinforcing fillers in polycarbonate (PC)/poly(vinylidene fluoride) (PVDF)-blend (designated CF)-based nanocomposites. Additionally, organo-montmorillonite (15A) was incorporated simultaneously with the individual carbon fillers to form hybrid filler nanocomposites. Microscopic images confirmed the selective localization of carbon fillers, mainly in the continuous PC phase, while 15A located in the PVDF domains. Differential scanning calorimetry results showed that blending PVDF with PC or forming single/double carbon filler composites resulted in lower PVDF crystallization temperature during cooling. However, PVDF crystallization was promoted by the inclusion of 15A, and the growth of β-form crystals was induced. The rigidity of the CF blend increased after the formation of nanocomposites. Among the three individually added carbon fillers, GnPs improved the CF moduli the most; the simultaneous loading of CNT/GnP resulted in the highest moduli by up to 33%/46% increases in tensile/flexural moduli, respectively, compared with those of the CF blend. Rheological viscosity results showed that adding CNTs increased the complex viscosity of the blend to a greater extent than did adding CB or GnPs, and the viscosity further increased after adding 15A. The electrical resistivity of the blend decreased with the inclusion of carbon fillers, particularly with CNT loading.